Support for creating .xcframework

* `make macOS` builds a universal framework
* `make xcframework` builds an .xcframework containing frameworks for macOS (universal), iOS, and iOS Simulator
* Addresses a compiler warning

src/Controls.cpp

@@ -253,6 +253,7 @@ int zts_restart()
 	_userCallbackMethodRef = _tmpUserCallbackMethodRef;
 	return zts_start(userProvidedPath.c_str(), NULL, userProvidedPort);
 #else
+    return ZTS_ERR_OK;
 	//return zts_start(userProvidedPath.c_str(), _tmpUserEventCallbackFunc, userProvidedPort);
 #endif
 }
@@ -415,4 +416,4 @@ void zts_delay_ms(long milliseconds)
 
 #ifdef __cplusplus
 }
-#endif
+#endif