Makefile: move -x objective-c option before filename

From the Clang documentation[1]:
> -x<language>, --language <arg>, --language=<arg>
> Treat subsequent input files as having type <language>

Follow the advice. Fixes #840.
[1]: https://clang.llvm.org/docs/ClangCommandLineReference.html

src/Makefile

@@ -508,7 +508,7 @@ core.o : core.c raylib.h rlgl.h utils.h raymath.h camera.h gestures.h
 
 # Compile rglfw module
 rglfw.o : rglfw.c
-	$(CC) -c $< $(CFLAGS) $(GLFW_CFLAGS) $(INCLUDE_PATHS) -D$(PLATFORM) -D$(GRAPHICS)
+	$(CC) $(CFLAGS) $(GLFW_CFLAGS) -c $<  $(INCLUDE_PATHS) -D$(PLATFORM) -D$(GRAPHICS)
 
 # Compile shapes module
 shapes.o : shapes.c raylib.h rlgl.h