ax_dump_events: enable ax_dump_events tool on mac

Bug: 1131921
Change-Id: I847df334df884624b2df8fa02b9dff2d80ca70fa
AX-Relnotes: n/a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2427310Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Alexander Surkov <asurkov@igalia.com>
Cr-Commit-Position: refs/heads/master@{#810276}

BUILD.gn

@@ -623,6 +623,7 @@ group("gn_all") {
       "//third_party/breakpad:dump_syms",
 
       # The following are accessibility API tools.
+      "//tools/accessibility/inspect:ax_dump_events",
       "//tools/accessibility/inspect:ax_dump_tree",
     ]
     deps -= [