List ssl_debug_helpers_generated.h in generated files

Running `generate_ssl_debug_helpers.py` generates both
`ssl_debug_helpers_generated.c` and `ssl_debug_helpers_generated.h`.

List the `.h` file as well as the `.c` file in `check-generated-files.sh` so
that `check-generated-files.sh -u` will complain if it isn't up to date.

List it in `Makefile` and `CMakeLists.txt` so that parallel builds know when
to wait until the `.h` file is present. In `Makefile`, declare the `.c` file
as depending on the `.h` file for order. This way, a dependency for either
will wait until the `.h` file is present, and since the `.h` file is
generated after the `.c` file, this guarantees that the `.c` file is
present.

This fixes random failures of `make -j` from a fresh checkout.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/library/CMakeLists.txt b/library/CMakeLists.txt
index add0784..1059e8c 100644
--- a/library/CMakeLists.txt
+++ b/library/CMakeLists.txt
@@ -147,6 +147,7 @@
 
     add_custom_command(
         OUTPUT
+            ${CMAKE_CURRENT_BINARY_DIR}/ssl_debug_helpers_generated.h
             ${CMAKE_CURRENT_BINARY_DIR}/ssl_debug_helpers_generated.c
         COMMAND
             ${MBEDTLS_PYTHON_EXECUTABLE}
@@ -161,6 +162,7 @@
     link_to_source(error.c)
     link_to_source(version_features.c)
     link_to_source(ssl_debug_helpers_generated.c)
+    link_to_source(ssl_debug_helpers_generated.h)
 endif()
 
 if(CMAKE_COMPILER_IS_GNUCC)