cmd/go: improve go build documentation
The existing documentation for `go help build` does not match the current behavior of `go build`. This commit fixes inconsistency between documentation and behavior as suggested in #60836 ticket.
Fixes #60836
Change-Id: I22f24f84815f50fecfa8c51b7f1c24e8e0cd8bc8
GitHub-Last-Rev:
7613930a3d6eb10fc61f29e4bf1b7b0fc9584cf8
GitHub-Pull-Request: golang/go#61438
Reviewed-on: https://go-review.googlesource.com/c/go/+/511015
Reviewed-by: qiulaidongfeng <2645477756@qq.com>
Auto-Submit: Bryan Mills <bcmills@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>