Add function to check whether or not we're part of an extension on Apple OSes

Change-Id: I308147c752ec9c869db87aa94ccf6c88e0999524
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>

src/corelib/kernel/qcore_mac_objc.mm

@@ -161,6 +161,12 @@ QDebug operator<<(QDebug debug, const QMacAutoReleasePool *pool)
 }
 #endif // !QT_NO_DEBUG_STREAM
 
+bool qt_apple_isApplicationExtension()
+{
+    static bool isExtension = [[NSBundle mainBundle] objectForInfoDictionaryKey:@"NSExtension"];
+    return isExtension;
+}
+
 #ifdef Q_OS_MACOS
 /*
     Ensure that Objective-C objects auto-released in main(), directly or indirectly,

src/corelib/kernel/qcore_mac_p.h

@@ -158,6 +158,7 @@ QDebug operator<<(QDebug debug, const QMacAutoReleasePool *pool);
 #endif
 
 Q_CORE_EXPORT void qt_apple_check_os_version();
+Q_CORE_EXPORT bool qt_apple_isApplicationExtension();
 
 // --------------------------------------------------------------------------