Fix build errors in CMake

tests/src/ssl_helpers.c depends on functions defined
in library/*.c. If it's complied as an OBJECT with other c files,
cmake complains undefined reference in link stage under programs/.
Therefore, tests/src/test_helpers/ is created to hold c files with
dependency of library/*.c. Besides, tests/src/test_helper/*.c is
separated into another OBJECT, mbedtls_test_helpers, as sources
to build all test suite executables.

In addition, everest header directory is included in case
MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED is enabled.

Signed-off-by: Yanray Wang <yanray.wang@arm.com>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 519604b..7bd9189 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -280,12 +280,23 @@
 # to define the test executables.
 #
 if(ENABLE_TESTING OR ENABLE_PROGRAMS)
-    file(GLOB MBEDTLS_TEST_FILES ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/*.c ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/drivers/*.c)
+    file(GLOB MBEDTLS_TEST_FILES
+         ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/*.c
+         ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/drivers/*.c)
     add_library(mbedtls_test OBJECT ${MBEDTLS_TEST_FILES})
     target_include_directories(mbedtls_test
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/tests/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
         PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/library)
+
+    file(GLOB MBEDTLS_TEST_HELPER_FILES
+         ${CMAKE_CURRENT_SOURCE_DIR}/tests/src/test_helpers/*.c)
+    add_library(mbedtls_test_helpers OBJECT ${MBEDTLS_TEST_HELPER_FILES})
+    target_include_directories(mbedtls_test_helpers
+        PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/tests/include
+        PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/include
+        PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/library
+        PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/3rdparty/everest/include)
 endif()
 
 if(ENABLE_PROGRAMS)
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 4549a7a..9bd93f1 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -237,7 +237,9 @@
             test_suite_${data_name}.datax
     )
 
-    add_executable(test_suite_${data_name} test_suite_${data_name}.c $<TARGET_OBJECTS:mbedtls_test>)
+    add_executable(test_suite_${data_name} test_suite_${data_name}.c
+                   $<TARGET_OBJECTS:mbedtls_test>
+                   $<TARGET_OBJECTS:mbedtls_test_helpers>)
     add_dependencies(test_suite_${data_name} ${dependency})
     target_link_libraries(test_suite_${data_name} ${libs})
     # Include test-specific header files from ./include and private header
diff --git a/tests/Makefile b/tests/Makefile
index 26947f4..75dc3c6 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -160,7 +160,7 @@
 $(MBEDLIBS):
 	$(MAKE) -C ../library
 
-MBEDTLS_TEST_OBJS=$(patsubst %.c,%.o,$(wildcard src/*.c src/drivers/*.c))
+MBEDTLS_TEST_OBJS=$(patsubst %.c,%.o,$(wildcard src/*.c src/drivers/*.c src/test_helpers/*.c))
 
 mbedtls_test: $(MBEDTLS_TEST_OBJS)
 
@@ -181,6 +181,10 @@
 	echo "  CC    $<"
 	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) -o $@ -c $<
 
+src/test_helpers/%.o : src/test_helpers/%.c
+	echo "  CC    $<"
+	$(CC) $(LOCAL_CFLAGS) $(CFLAGS) -o $@ -c $<
+
 C_FILES := $(addsuffix .c,$(APPS))
 c: $(C_FILES)
 
@@ -217,7 +221,7 @@
 clean:
 ifndef WINDOWS
 	rm -rf $(BINARIES) *.c *.datax
-	rm -f src/*.o src/drivers/*.o src/libmbed*
+	rm -f src/*.o src/drivers/*.o src/test_helpers/*.o src/libmbed*
 	rm -f include/test/instrument_record_status.h
 	rm -f include/alt-extra/*/*_alt.h
 	rm -rf libtestdriver1
@@ -228,6 +232,7 @@
 	if exist *.datax del /Q /F *.datax
 	if exist src/*.o del /Q /F src/*.o
 	if exist src/drivers/*.o del /Q /F src/drivers/*.o
+	if exist src/test_helpers/*.o del /Q /F src/test_helpers/*.o
 	if exist src/libmbed* del /Q /F src/libmed*
 	if exist include/test/instrument_record_status.h del /Q /F include/test/instrument_record_status.h
 endif
diff --git a/tests/src/ssl_helpers.c b/tests/src/test_helpers/ssl_helpers.c
similarity index 100%
rename from tests/src/ssl_helpers.c
rename to tests/src/test_helpers/ssl_helpers.c