fs: Follow up to the initial getexecpath() support

- Add missing CMake piece
- Fix logic to quiet warning

include/build_config/SDL_build_config.h.cmake

@@ -73,6 +73,7 @@
 #cmakedefine HAVE_DLOPEN 1
 #cmakedefine HAVE_MALLOC 1
 #cmakedefine HAVE_FDATASYNC 1
+#cmakedefine HAVE_GETEXECPATH 1
 #cmakedefine HAVE_GETENV 1
 #cmakedefine HAVE_GETHOSTNAME 1
 #cmakedefine HAVE_SETENV 1

src/filesystem/unix/SDL_sysfilesystem.c

@@ -71,7 +71,7 @@ static char *readSymLink(const char *path)
     return NULL;
 }
 
-#ifdef SDL_PLATFORM_OPENBSD
+#if defined(SDL_PLATFORM_OPENBSD) && !defined(HAVE_GETEXECPATH)
 static char *search_path_for_binary(const char *bin)
 {
     const char *envr_real = SDL_getenv("PATH");