Export main() when building for android

src/app/main.cpp

@@ -400,6 +400,11 @@ void myMessageOutput( QtMsgType type, const char *msg )
   }
 }
 
+#if(ANDROID)
+// On Android, there there is a libqgis.so instead of a qgis executable.
+// The main method symbol of this library needs to be exported so it can be called by java
+APP_EXPORT
+#endif
 int main( int argc, char *argv[] )
 {
 #ifdef Q_OS_MACX