cmd/coordinator: fix retry-forever loop in trybots if cross-compiled make.bash fails
cmd/coordinator: fix retry-forever loop in trybots if cross-compiled make.bash fails

Change-Id: Ia57133aea1c9d7b6b8bd9345efeeefbfc13d75e5
Reviewed-on: https://go-review.googlesource.com/38461
Reviewed-by: Cherry Zhang <d62e63aa42ce272d7b6a5055d97e942b33a34679@google.com>

golang/build,golang/build,golang/build,golang/build