Fixed bug 2812 - Make libSDL2main.a usable on Android via a dummy symbol

Jonas Kulla

This eliminates the need to manually compile in SDL_main_android.c.
Instead, add "-lSDL2main -Wl,-u,SDL_main_dummy" when linking.

I don't know how the nkd-build process works, but unless it was
for some reason linking libSDL2main.a it should be unaffected.

src/main/android/SDL_android_main.c

@@ -15,6 +15,9 @@
 *******************************************************************************/
 #include <jni.h>
 
+/* Dummy symbol so '-u SDL_main_dummy' forces ld to link in libSDL2main.a */
+JNIEXPORT int SDL_main_dummy;
+
 /* Called before SDL_main() to initialize JNI bindings in SDL library */
 extern void SDL_Android_Init(JNIEnv* env, jclass cls);