tests: Use parent module includes when used as a submodule

For Makefiles, enable overriding where includes can come from in order
to enable the parent module to set the include path. This allows the
parent module to specify that its config.h should be used, even when the
submodule when built standalone would use a different config.h.

For CMake, always look in the parent's include folder and our own. List
the parent's include folder first, so that preference is given to parent
include files.

tests/CMakeLists.txt

@@ -43,6 +43,10 @@ function(add_test_suite suite_name)
     include_directories(${CMAKE_CURRENT_SOURCE_DIR})
     add_executable(test_suite_${data_name} test_suite_${data_name}.c)
     target_link_libraries(test_suite_${data_name} ${libs})
+    target_include_directories(test_suite_${data_name}
+        PUBLIC ${CMAKE_SOURCE_DIR}/include/
+        PUBLIC ${CMAKE_SOURCE_DIR}/crypto/include/)
+
     if(${data_name} MATCHES ${SKIP_TEST_SUITES_REGEX})
         message(STATUS "The test suite ${data_name} will not be executed.")
     else()

tests/Makefile

@@ -6,7 +6,8 @@ CFLAGS	?= -O2
 WARNING_CFLAGS ?= -Wall -W -Wdeclaration-after-statement -Wno-unused-function -Wno-unused-value
 LDFLAGS ?=
 
-LOCAL_CFLAGS = $(WARNING_CFLAGS) -I../include -I../library -D_FILE_OFFSET_BITS=64
+CRYPTO_INCLUDES ?= -I../include
+LOCAL_CFLAGS = $(WARNING_CFLAGS) $(CRYPTO_INCLUDES) -I../library -D_FILE_OFFSET_BITS=64
 LOCAL_LDFLAGS = -L../library			\
 		-lmbedtls$(SHARED_SUFFIX)	\
 		-lmbedx509$(SHARED_SUFFIX)	\