test: Run selected noninteractive tests at build-time

In Autotools, these are run by `make -C ${builddir}/test check`.
In CMake, they're run by `make -C ${builddir} test` or
`ninja -C ${builddir} test` or `ctest --test-dir ${builddir}`.

Signed-off-by: Simon McVittie <smcv@collabora.com>

CMakeLists.txt

@@ -2980,6 +2980,7 @@ set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -DSDL_BUILD_MICRO_VERSION=${SDL_MICRO_VERSIO
 ##### Tests #####
 
 if(SDL_TEST)
+  include(CTest)
   include_directories(BEFORE "${SDL2_BINARY_DIR}/include")
   include_directories(AFTER "${SDL2_SOURCE_DIR}/include")
   file(GLOB TEST_SOURCES ${SDL2_SOURCE_DIR}/src/test/*.c)