Remove MacOS from traffic annotations

- Don't build traffic_annotation_auditor on MacOS.
- Remove "mac" from the "os_list" everywhere in annotations.xml.
- Add a warning and fail on buildbots when an unsupported platform is
  added in annotations.xml.

Bug: 878760
Change-Id: I7329e8ca2940880cdc4aa357acd42b2976d9a80e
Reviewed-on: https://chromium-review.googlesource.com/c/1287097
Reviewed-by: Ramin Halavati <[email protected]>
Reviewed-by: John Budorick <[email protected]>
Commit-Queue: Nicolas Ouellet-Payeur <[email protected]>
Cr-Commit-Position: refs/heads/master@{#601147}
diff --git a/BUILD.gn b/BUILD.gn
index a149772..a5c1f1b8 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -147,8 +147,6 @@
       "//third_party/pdfium/samples:pdfium_test",
       "//third_party/webrtc/rtc_tools:frame_analyzer",
       "//tools/perf/clear_system_cache",
-      "//tools/traffic_annotation/auditor:traffic_annotation_auditor",
-      "//tools/traffic_annotation/auditor:traffic_annotation_auditor_unittests",
       "//ui/accessibility:accessibility_unittests",
       "//ui/accessibility/extensions",
     ]
@@ -276,6 +274,13 @@
     ]
   }
 
+  if (is_win || is_linux) {
+    deps += [
+      "//tools/traffic_annotation/auditor:traffic_annotation_auditor",
+      "//tools/traffic_annotation/auditor:traffic_annotation_auditor_unittests",
+    ]
+  }
+
   if (is_mac) {
     deps += [ "//chrome/installer/gcapi_mac:gcapi_example" ]
   }