Android: Enforce native style

We use the 'default' style extraction option introduced in Qt 5.12.
With this setting, Qt 5.12.3 does indeed extract the style but
doesn't set the variable which would activate the style.
Resolves the Android aspect of GH-1255.

Author: dg0yt

src/main.cpp

@@ -112,6 +112,10 @@ int main(int argc, char** argv)
 	QApplication qapp(argc, argv);
 #endif
 
+#ifdef Q_OS_ANDROID
+	qputenv("QT_USE_ANDROID_NATIVE_STYLE", "1");
+#endif
+	
 	// Load resources
 	Q_INIT_RESOURCE(resources);