[demos] Add push make target
[demos] Add push make target

Change-Id: I515ab023748f032726ed0427af22852a2602e476
Reviewed-on: https://skia-review.googlesource.com/c/buildbot/+/418557
Auto-Submit: Kevin Lubick <7cdab2cfab351f23814786ba39716e90eed69047@google.com>
Reviewed-by: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@google.com>
Commit-Queue: Ravi Mistry <9fa2e7438b8cb730f96b74865492597170561628@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