Add tests to mac-arm64 builder

These will not actually be executed, but should be isolated, which is
useful for the testing team.

Bug: 1106083
Change-Id: Ie9094bf7eaa70dd0a130ccb747c7f64d8f5bdffd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2339921
Auto-Submit: Stephen Martinis <martiniss@chromium.org>
Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Erik Staab <estaab@chromium.org>
Commit-Queue: Stephen Martinis <martiniss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#795165}

testing/buildbot/waterfalls.pyl

@@ -2330,6 +2330,10 @@
         'additional_compile_targets': [
           'all',
         ],
+        'test_suites': {
+          'gtest_tests': 'chromium_mac_gtests_no_nacl',
+          'isolated_scripts': 'chromium_mac_rel_isolated_scripts',
+        },
       },
       'mac-code-coverage': {
         'mixins': [