go/build: remove unnecessary copies of package variables
These variables never change, we don't need second copies of them.
Also rename bPlusBuild to plusBuild, since it is the only remaining
variable with a "b" prefix.
Change-Id: I97089b001d23e9b0f2096e19d9ceed7a9bbb377d
Reviewed-on: https://go-review.googlesource.com/c/go/+/429636
TryBot-Result: Gopher Robot <gobot@golang.org> Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org> Reviewed-by: Benny Siegert <bsiegert@gmail.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>