[bazel] Do not build GrVkSecondaryCBDrawContext by default

See also http://cl/501820380

I'm not making this a flag in .bazelrc because no clients
should use this (except for Chromium in Android WebView).
We only need to turn it on for tests.

Change-Id: I54a991b576ea8893dd3d0976860bd46c315f36a2
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/629756
Reviewed-by: Herb Derby <herb@google.com>
3 files changed