Add SDL3 3.1.1-preview

libs/SDL3/cmake/test/main_cli.c

@@ -0,0 +1,15 @@
+#define SDL_MAIN_HANDLED
+#include <SDL3/SDL.h>
+#include <SDL3/SDL_main.h>
+
+int main(int argc, char *argv[])
+{
+    SDL_SetMainReady();
+    if (SDL_Init(0) < 0) {
+        SDL_Log("Could not initialize SDL: %s\n", SDL_GetError());
+        return 1;
+    }
+    SDL_Delay(100);
+    SDL_Quit();
+    return 0;
+}