[tools] Add minor_mc test variant to the V8 CQ

R=machenbach@chromium.org

Bug: chromium:651354
Change-Id: I9ce5c6dc6a155ff9a70713cbdbf2d4037ad47f24
Reviewed-on: https://chromium-review.googlesource.com/1053773
Commit-Queue: Sergiy Byelozyorov <sergiyb@chromium.org>
Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53214}

infra/testing/builders.pyl

@@ -142,6 +142,7 @@
       {'name': 'test262_variants', 'variant': 'extra', 'shards': 3},
       {'name': 'v8testing', 'shards': 3},
       {'name': 'v8testing', 'variant': 'extra', 'shards': 2},
+      {'name': 'v8testing', 'variant': 'minor_mc', 'shards': 1},
     ],
   },
   'v8_linux64_fyi_rel_ng_triggered': {