make.bat, make.rc: show bootstrap toolchain version
Print the bootstrap toolchain version on Plan 9 and Windows,
same as on all Unix systems since CL 204757 (Nov 2019).
This makes it easier to see what is going on in a build.
For #44505.
Change-Id: I50cdd5e15a7c8b908e33e92780f8a3bca65c91ef
Reviewed-on: https://go-review.googlesource.com/c/go/+/419452 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Russ Cox <rsc@golang.org>
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>