Merge #16720: qt: Replace objc_msgSend() function calls with the native Objective-C syntax

0bb33b5348 qt: Replace objc_msgSend with native syntax (Hennadii Stepanov)

Pull request description:

  Changes in Xcode 11 Objective-C Runtime cause an error (#16387) during building on MacOS 10.15 Catalina.

  This PR fixes this issue by replacing `objc_msgSend()` function calls with the native Objective-C syntax.

  Refs:
  - [changes in `objc_msgSend` function](https://developer.apple.com/documentation/objectivec/1456712-objc_msgsend?changes=latest_minor&language=objc)
  - [`OBJC_OLD_DISPATCH_PROTOTYPES` macro](https://developer.apple.com/documentation/objectivec/objc_old_dispatch_prototypes?language=objc)

ACKs for top commit:
  l2a5b1:
    ACK 0bb33b5 - Diff looks good. Sending messages via native Objective-C code feels more robust and is more readable than casting all the `objc_msgSend` function calls to the appropriate function signature (which would also have fixed the issue).
  jonasschnelli:
    utACK 0bb33b5348 - Confirmed that the called macOS framework function is available on our build targets.
  fanquake:
    ACK 0bb33b5348 - Still works as expected.

Tree-SHA512: c09cb684d06bd1da053a17c182b7bb1642e45bb347d26c76e1c5d835c320567caee366d85e34bb7f2be38e63ed041e0d06a56c2a9d89f7e5bece9b19cc5c6772

src/qt/guiutil.cpp

@@ -57,9 +57,10 @@
 #pragma GCC diagnostic push
 #pragma GCC diagnostic ignored "-Wdeprecated-declarations"
 
-#include <objc/objc-runtime.h>
 #include <CoreServices/CoreServices.h>
 #include <QProcess>
+
+void ForceActivation();
 #endif
 
 namespace GUIUtil {
@@ -359,10 +360,7 @@ bool isObscured(QWidget *w)
 void bringToFront(QWidget* w)
 {
 #ifdef Q_OS_MAC
-    // Force application activation on macOS. With Qt 5.4 this is required when
-    // an action in the dock menu is triggered.
-    id app = objc_msgSend((id) objc_getClass("NSApplication"), sel_registerName("sharedApplication"));
-    objc_msgSend(app, sel_registerName("activateIgnoringOtherApps:"), YES);
+    ForceActivation();
 #endif
 
     if (w) {