cmd/go: breakage with go version command and GOFLAGS environment variable [1.15 backport]

[gopherbot]

@mvdan requested issue #41264 to be considered for backport to the next 1.15 minor release.

@gopherbot please consider this for backport to 1.15, it's a regression.

[mvdan]

@andybons @dmitshur I assume I need approval from someone for this backport, as per https://github.com/golang/go/wiki/MinorReleases.

[mvdan]

CL, since the bot seems to not pick it up: https://go-review.googlesource.com/c/go/+/255498

[gopherbot]

Change https://golang.org/cl/255498 mentions this issue: [release-branch.go1.15] cmd/go: relax version's error on unexpected flags

[cagedmantis]

Approved because this is a serious issue without a workaround.

[mvdan]

@cagedmantis can I merge the backport CL, then? Or should someone else do it?

[dmitshur]

@mvdan From https://golang.org/wiki/MinorReleases:

Gerrit is configured to only allow release managers to submit to release branches,

Submitting the CL is a step that release managers are responsible for. We’ll get to it as soon as we can.

[gopherbot]

Closed by merging 8841790 to release-branch.go1.15.