Back up and restore config.h systematically

In all.sh, always save config.h before running a component, instead of
doing it manually in each component that requires it (except when we
forget, which has happened). This would break a script that requires
config.h.bak not to exist, but we don't have any of those.
diff --git a/tests/scripts/all.sh b/tests/scripts/all.sh
index 5dd2acf..d63a948 100755
--- a/tests/scripts/all.sh
+++ b/tests/scripts/all.sh
@@ -529,7 +529,6 @@
 
 component_test_sslv3 () {
     msg "build: Default + SSLv3 (ASan build)" # ~ 6 min
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_SSL_PROTO_SSL3
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
     make
@@ -547,7 +546,6 @@
 
 component_test_no_renegotiation () {
     msg "build: Default + !MBEDTLS_SSL_RENEGOTIATION (ASan build)" # ~ 6 min
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl unset MBEDTLS_SSL_RENEGOTIATION
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
     make
@@ -561,7 +559,6 @@
 
 component_test_rsa_no_crt () {
     msg "build: Default + RSA_NO_CRT (ASan build)" # ~ 6 min
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_RSA_NO_CRT
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
     make
@@ -578,7 +575,6 @@
 
 component_test_small_ssl_out_content_len () {
     msg "build: small SSL_OUT_CONTENT_LEN (ASan build)"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_SSL_IN_CONTENT_LEN 16384
     scripts/config.pl set MBEDTLS_SSL_OUT_CONTENT_LEN 4096
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
@@ -590,7 +586,6 @@
 
 component_test_small_ssl_in_content_len () {
     msg "build: small SSL_IN_CONTENT_LEN (ASan build)"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_SSL_IN_CONTENT_LEN 4096
     scripts/config.pl set MBEDTLS_SSL_OUT_CONTENT_LEN 16384
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
@@ -602,7 +597,6 @@
 
 component_test_small_ssl_dtls_max_buffering () {
     msg "build: small MBEDTLS_SSL_DTLS_MAX_BUFFERING #0"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_SSL_DTLS_MAX_BUFFERING 1000
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
     make
@@ -613,7 +607,6 @@
 
 component_test_small_mbedtls_ssl_dtls_max_buffering () {
     msg "build: small MBEDTLS_SSL_DTLS_MAX_BUFFERING #1"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_SSL_DTLS_MAX_BUFFERING 240
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
     make
@@ -624,7 +617,6 @@
 
 component_test_full_cmake_clang () {
     msg "build: cmake, full config, clang" # ~ 50s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # too slow for tests
     CC=clang cmake -D CMAKE_BUILD_TYPE:String=Check -D ENABLE_TESTING=On .
@@ -645,7 +637,6 @@
 
 component_build_deprecated () {
     msg "build: make, full config + DEPRECATED_WARNING, gcc -O" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl set MBEDTLS_DEPRECATED_WARNING
     # Build with -O -Wextra to catch a maximum of issues.
@@ -699,7 +690,6 @@
     # This should catch missing mbedtls_printf definitions, and by disabling file
     # IO, it should catch missing '#include <stdio.h>'
     msg "build: full config except platform/fsio/net, make, gcc, C99" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_PLATFORM_C
     scripts/config.pl unset MBEDTLS_NET_C
@@ -721,7 +711,6 @@
 component_build_no_std_function () {
     # catch compile bugs in _uninit functions
     msg "build: full config with NO_STD_FUNCTION, make, gcc" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl set MBEDTLS_PLATFORM_NO_STD_FUNCTIONS
     scripts/config.pl unset MBEDTLS_ENTROPY_NV_SEED
@@ -730,7 +719,6 @@
 
 component_build_no_ssl_srv () {
     msg "build: full config except ssl_srv.c, make, gcc" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_SSL_SRV_C
     make CC=gcc CFLAGS='-Werror -Wall -Wextra -O0'
@@ -738,7 +726,6 @@
 
 component_build_no_ssl_cli () {
     msg "build: full config except ssl_cli.c, make, gcc" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_SSL_CLI_C
     make CC=gcc CFLAGS='-Werror -Wall -Wextra -O0'
@@ -748,7 +735,6 @@
     # Note, C99 compliance can also be tested with the sockets support disabled,
     # as that requires a POSIX platform (which isn't the same as C99).
     msg "build: full config except net_sockets.c, make, gcc -std=c99 -pedantic" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_NET_C # getaddrinfo() undeclared, etc.
     scripts/config.pl set MBEDTLS_NO_PLATFORM_ENTROPY # uses syscall() on GNU/Linux
@@ -758,7 +744,6 @@
 component_test_no_max_fragment_length () {
     # Run max fragment length tests with MFL disabled
     msg "build: default config except MFL extension (ASan build)" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl unset MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
     CC=gcc cmake -D CMAKE_BUILD_TYPE:String=Asan .
     make
@@ -769,7 +754,6 @@
 
 component_test_no_max_fragment_length_small_ssl_out_content_len () {
     msg "build: no MFL extension, small SSL_OUT_CONTENT_LEN (ASan build)"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl unset MBEDTLS_SSL_MAX_FRAGMENT_LENGTH
     scripts/config.pl set MBEDTLS_SSL_IN_CONTENT_LEN 16384
     scripts/config.pl set MBEDTLS_SSL_OUT_CONTENT_LEN 4096
@@ -782,7 +766,6 @@
 
 component_test_null_entropy () {
     msg "build: default config with  MBEDTLS_TEST_NULL_ENTROPY (ASan build)"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_TEST_NULL_ENTROPY
     scripts/config.pl set MBEDTLS_NO_DEFAULT_ENTROPY_SOURCES
     scripts/config.pl set MBEDTLS_ENTROPY_C
@@ -798,7 +781,6 @@
 
 component_test_platform_calloc_macro () {
     msg "build: MBEDTLS_PLATFORM_{CALLOC/FREE}_MACRO enabled (ASan build)"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_PLATFORM_MEMORY
     scripts/config.pl set MBEDTLS_PLATFORM_CALLOC_MACRO calloc
     scripts/config.pl set MBEDTLS_PLATFORM_FREE_MACRO   free
@@ -811,7 +793,6 @@
 
 component_test_aes_fewer_tables () {
     msg "build: default config with AES_FEWER_TABLES enabled"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_AES_FEWER_TABLES
     make CC=gcc CFLAGS='-Werror -Wall -Wextra'
 
@@ -821,7 +802,6 @@
 
 component_test_aes_rom_tables () {
     msg "build: default config with AES_ROM_TABLES enabled"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_AES_ROM_TABLES
     make CC=gcc CFLAGS='-Werror -Wall -Wextra'
 
@@ -831,7 +811,6 @@
 
 component_test_aes_fewer_tables_and_rom_tables () {
     msg "build: default config with AES_ROM_TABLES and AES_FEWER_TABLES enabled"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_AES_FEWER_TABLES
     scripts/config.pl set MBEDTLS_AES_ROM_TABLES
     make CC=gcc CFLAGS='-Werror -Wall -Wextra'
@@ -848,7 +827,6 @@
 component_test_m32_o0 () {
     # Build once with -O0, to compile out the i386 specific inline assembly
     msg "build: i386, make, gcc -O0 (ASan build)" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     make CC=gcc CFLAGS='-O0 -Werror -Wall -Wextra -m32 -fsanitize=address'
 
@@ -859,7 +837,6 @@
 component_test_m32_o1 () {
     # Build again with -O1, to compile in the i386 specific inline assembly
     msg "build: i386, make, gcc -O1 (ASan build)" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     make CC=gcc CFLAGS='-O1 -Werror -Wall -Wextra -m32 -fsanitize=address'
 
@@ -869,7 +846,6 @@
 
 component_test_mx32 () {
     msg "build: 64-bit ILP32, make, gcc" # ~ 30s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     make CC=gcc CFLAGS='-Werror -Wall -Wextra -mx32'
 
@@ -879,7 +855,6 @@
 
 component_test_have_int32 () {
     msg "build: gcc, force 32-bit bignum limbs"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl unset MBEDTLS_HAVE_ASM
     scripts/config.pl unset MBEDTLS_AESNI_C
     scripts/config.pl unset MBEDTLS_PADLOCK_C
@@ -891,7 +866,6 @@
 
 component_test_have_int64 () {
     msg "build: gcc, force 64-bit bignum limbs"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl unset MBEDTLS_HAVE_ASM
     scripts/config.pl unset MBEDTLS_AESNI_C
     scripts/config.pl unset MBEDTLS_PADLOCK_C
@@ -903,7 +877,6 @@
 
 component_test_no_udbl_division () {
     msg "build: MBEDTLS_NO_UDBL_DIVISION native" # ~ 10s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # too slow for tests
     scripts/config.pl set MBEDTLS_NO_UDBL_DIVISION
@@ -915,7 +888,6 @@
 
 component_test_no_64bit_multiplication () {
     msg "build: MBEDTLS_NO_64BIT_MULTIPLICATION native" # ~ 10s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_MEMORY_BACKTRACE # too slow for tests
     scripts/config.pl set MBEDTLS_NO_64BIT_MULTIPLICATION
@@ -927,7 +899,6 @@
 
 component_build_arm_none_eabi_gcc () {
     msg "build: arm-none-eabi-gcc, make" # ~ 10s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_NET_C
     scripts/config.pl unset MBEDTLS_TIMING_C
@@ -945,7 +916,6 @@
 
 component_build_arm_none_eabi_gcc_no_udbl_division () {
     msg "build: arm-none-eabi-gcc -DMBEDTLS_NO_UDBL_DIVISION, make" # ~ 10s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_NET_C
     scripts/config.pl unset MBEDTLS_TIMING_C
@@ -966,7 +936,6 @@
 
 component_build_arm_none_eabi_gcc_no_64bit_multiplication () {
     msg "build: arm-none-eabi-gcc MBEDTLS_NO_64BIT_MULTIPLICATION, make" # ~ 10s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_NET_C
     scripts/config.pl unset MBEDTLS_TIMING_C
@@ -987,7 +956,6 @@
 
 component_build_armcc () {
     msg "build: ARM Compiler 5, make"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl full
     scripts/config.pl unset MBEDTLS_NET_C
     scripts/config.pl unset MBEDTLS_TIMING_C
@@ -1028,7 +996,6 @@
 
 component_test_allow_sha1 () {
     msg "build: allow SHA1 in certificates by default"
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl set MBEDTLS_TLS_DEFAULT_ALLOW_SHA1_IN_CERTIFICATES
     make CFLAGS='-Werror -Wall -Wextra'
     msg "test: allow SHA1 in certificates by default"
@@ -1052,7 +1019,6 @@
 
 component_test_memsan () {
     msg "build: MSan (clang)" # ~ 1 min 20s
-    cp "$CONFIG_H" "$CONFIG_BAK"
     scripts/config.pl unset MBEDTLS_AESNI_C # memsan doesn't grok asm
     CC=clang cmake -D CMAKE_BUILD_TYPE:String=MemSan .
     make
@@ -1242,6 +1208,9 @@
     if [ $ALL_EXCEPT -ne 0 ] && component_is_excluded "$1"; then
         return
     fi
+    # Back up the configuration in case the component modifies it.
+    # The cleanup function will restore it.
+    cp -p "$CONFIG_H" "$CONFIG_BAK"
     current_component="$1"
     "$@"
     cleanup