[gold] Clean frontend build
[gold] Clean frontend build

Change-Id: I9d144d51451f04e9eb9f5083fb2fa880babea515
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/373659
Reviewed-by: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>

google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot,google/skia-buildbot