Remove rtc_base_approved_objc and introduce rtc_base:logging_mac.

This CL removes the need of having rtc_base:rtc_base_approved_generic
and rtc_base:rtc_base_approved_objc since it removes the _objc build
target by moving the declaration of rtc::DescriptionFromOSStatus into
rtc_base/logging_mac.h in order to have a new target
rtc_base:logging_mac on which rtc_base:logging can depend on.

The target rtc_base:rtc_base_approved_generic will be removed in a
follow up CL.

Bug: webrtc:9838
Change-Id: Id93ac7bced213128e7d654694ff15337c26dab62
Reviewed-on: https://webrtc-review.googlesource.com/c/104802
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25085}
diff --git a/rtc_base/BUILD.gn b/rtc_base/BUILD.gn
index 140d2ff..22a3507 100644
--- a/rtc_base/BUILD.gn
+++ b/rtc_base/BUILD.gn
@@ -85,9 +85,6 @@
     ":thread_checker",
     ":timeutils",
   ]
-  if (is_mac && !build_with_chromium) {
-    public_deps += [ ":rtc_base_approved_objc" ]
-  }
 }
 
 rtc_source_set("macromagic") {
@@ -220,6 +217,10 @@
     ]
     deps += [ "system:inline" ]
 
+    if (is_mac) {
+      deps += [ ":logging_mac" ]
+    }
+
     # logging.h needs the deprecation header while downstream projects are
     # removing code that depends on logging implementation details.
     deps += [ ":deprecation" ]
@@ -488,20 +489,13 @@
 }
 
 if (is_mac && !build_with_chromium) {
-  config("rtc_base_approved_objc_all_dependent_config") {
-    visibility = [ ":rtc_base_approved_objc" ]
-    libs = [ "Foundation.framework" ]  # needed for logging_mac.mm
-  }
-
-  rtc_source_set("rtc_base_approved_objc") {
-    visibility = [ ":rtc_base_approved" ]
-    all_dependent_configs = [ ":rtc_base_approved_objc_all_dependent_config" ]
+  rtc_source_set("logging_mac") {
+    visibility = [ ":logging" ]
+    libs = [ "Foundation.framework" ]
     sources = [
+      "logging_mac.h",
       "logging_mac.mm",
     ]
-    deps = [
-      ":logging",
-    ]
   }
 }