cmd/dist: don't pass -linkmode=auto
This is the default value of this flag, so passing it clutters up
debugging output. This also makes it clearer which tests are running
with a default configuration.
Change-Id: If793934829c79f087c7a6e3fa8f64dc33959c213
Reviewed-on: https://go-review.googlesource.com/c/go/+/496176
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>