cmake HAVE_ATTRIBUTE_UNINITIALIZED examples

Ravbug/UnityHubNative wxWidgets/3rdparty/pcre/CMakeLists.txt :182

check_c_source_compiles(
  "int main(void) { char buf[128] __attribute__((uninitialized)); (void)buf; return 0; }"
  HAVE_ATTRIBUTE_UNINITIALIZED
)