cmd/go: only run -race test if -race works
cmd/go: only run -race test if -race works

Updates #23694

Change-Id: I5fdad8cceacb8bbc85ca2661eb6482aa80343656
Reviewed-on: https://go-review.googlesource.com/92075
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

cloudflare/go,codestation/go,CAFxX/go,josharian/go,cloudflare/go,codestation/go,golang/go,cloudflare/go,CAFxX/go,codestation/go,CAFxX/go,golang/go,akutz/go,cloudflare/go,golang/go,josharian/go,akutz/go,Cofyc/go,nawawi/go,josharian/go,josharian/go,CAFxX/go,Cofyc/go,codestation/go,Cofyc/go,josharian/go,akutz/go,akutz/go,akutz/go,Cofyc/go,CAFxX/go,cloudflare/go,codestation/go,CAFxX/go,nawawi/go,josharian/go,cloudflare/go,josharian/go,nawawi/go,nawawi/go,akutz/go,CAFxX/go,christopher-henderson/Go,Cofyc/go,cloudflare/go,codestation/go,nawawi/go,Cofyc/go,golang/go,CAFxX/go,codestation/go,golang/go,Cofyc/go,nawawi/go,akutz/go,golang/go,codestation/go,cloudflare/go,golang/go,golang/go,Cofyc/go,nawawi/go,nawawi/go,akutz/go,josharian/go