Merge pull request #4227 from ligfx/clean_objc

Don't force compile everything as Objective-C++ on macOS

Source/Core/Common/CMakeLists.txt

@@ -82,7 +82,7 @@ endif()
 if(WIN32)
     set(SRCS ${SRCS} GL/GLInterface/WGL.cpp)
 elseif(APPLE)
-    set(SRCS ${SRCS} GL/GLInterface/AGL.cpp)
+    set(SRCS ${SRCS} GL/GLInterface/AGL.mm)
 elseif(USE_X11)
     if (NOT USE_EGL)
         set(SRCS ${SRCS} GL/GLInterface/GLX.cpp)

Source/Core/Common/GL/GLInterface/AGL.h

@@ -4,8 +4,11 @@
 
 #pragma once
 
-#ifdef __APPLE__
+#if defined(__APPLE__) && defined(__OBJC__)
 #import <AppKit/AppKit.h>
+#else
+struct NSOpenGLContext;
+struct NSView;
 #endif
 
 #include "Common/GL/GLInterfaceBase.h"