As some callers don't have a testing context, modify testenv.Executable
to accept nil (similar to how testenv.GOROOT works).
Change-Id: I39112a7869933785a26b5cb6520055b3cc42b847
Reviewed-on: https://go-review.googlesource.com/c/go/+/609835 Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>