Add CI job for bazelbuild/bazel-toolchains repo.
Add CI job for bazelbuild/bazel-toolchains repo.

Change-Id: I8eb654dc18faf4c97470823c09fb1b9250f830c5

bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration,bazelbuild/continuous-integration