Add missing dependency on Foundation.framework

Currently it's provided transitively/accidentally.
Without it, there's an error:

Undefined symbols for architecture x86_64:
  "_objc_msgSend", referenced from:
      message_center::MessagePopupView::GetOpacity() const in message_popup_view_mac.o

Change-Id: Ic890ab72be9f1523045e518556abeda8be73a75a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1730415Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Oleh Prypin <oprypin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683348}

ui/message_center/BUILD.gn

@@ -129,6 +129,9 @@ jumbo_component("message_center") {
         "//ui/events",
         "//ui/views",
       ]
+      if (is_mac) {
+        libs = [ "Foundation.framework" ]
+      }
     }
   } else {
     # Notification service disabled.