cmake: build tests against installed SDL prefix

test/testautomation_intrinsics.c

@@ -2,8 +2,10 @@
  * Intrinsics test suite
  */
 
+#ifndef NO_BUILD_CONFIG
 /* Disable intrinsics that are unsupported by the current compiler */
 #include <build_config/SDL_build_config.h>
+#endif
 
 #include <SDL3/SDL.h>
 #include <SDL3/SDL_intrin.h>