Fix QGLWidget viewport resize on macOS

This fixes #2092, a long-standing bug where on macOS resizing the window
results in a garbled display.

It seems the seemingly optional child()->makeCurrent call is actually
required on macOS. Enabling it in all cases fixes the resize issue.

src/citra_qt/bootmanager.cpp

@@ -128,13 +128,14 @@ void GRenderWindow::moveContext() {
 }
 
 void GRenderWindow::SwapBuffers() {
-#if !defined(QT_NO_DEBUG)
-    // Qt debug runtime prints a bogus warning on the console if you haven't called makeCurrent
-    // since the last time you called swapBuffers. This presumably means something if you're using
-    // QGLWidget the "regular" way, but in our multi-threaded use case is harmless since we never
-    // call doneCurrent in this thread.
+    // In our multi-threaded QGLWidget use case we shouldn't need to call `makeCurrent`,
+    // since we never call `doneCurrent` in this thread.
+    // However:
+    // - The Qt debug runtime prints a bogus warning on the console if `makeCurrent` wasn't called
+    // since the last time `swapBuffers` was executed;
+    // - On macOS, if `makeCurrent` isn't called explicitely, resizing the buffer breaks.
     child->makeCurrent();
-#endif
+
     child->swapBuffers();
 }