cmd/go: skip some tests that run builds in short mode

cmd/go: skip some tests that run builds in short mode

cmd/go tests that run builds are generally skipped in short mode. This
change will adds skips for some tests that were running builds.

I found these by sorting tests by elapsed time and removing the top
tests that invoked go build. It's our practice to skip tests that run go
build without the -n flag (which prints but doesn't execute commands).

On my work laptop this reduces test run time from about 20 seconds to
about 16 seconds. On my linux workstation it reduces test run time from
about 10 seconds to about 5 seconds.

Change-Id: I18ffcc231df013cb6ac5f5eb3544bed28dadeda8
Reviewed-on: https://go-review.googlesource.com/c/go/+/653775
Reviewed-by: Alan Donovan <adonovan@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>