Use #ifdef/#ifndef instead of #if defined/#if \!defined

src/misc/unix/SDL_sysurl.c

@@ -37,7 +37,7 @@ int SDL_SYS_OpenURL(const char *url)
 {
     const pid_t pid1 = fork();
     if (pid1 == 0) { /* child process */
-#if defined(USE_POSIX_SPAWN)
+#ifdef USE_POSIX_SPAWN
         pid_t pid2;
         const char *args[] = { "xdg-open", url, NULL };
         /* Clear LD_PRELOAD so Chrome opens correctly when this application is launched by Steam */