cmd/go: adjust regexp that cleans cgo-related errors
cmd/go: adjust regexp that cleans cgo-related errors

The compiler now also prints column information - make sure we use
the correct regexp for compiler error cleanups. Accept both, error
positions with columns and without, since column printing may be
disabled with -gcflags=-C.

Fixes #20628.

Change-Id: I46dc921dd5c29d7b8172cd19a3df57951f60d889
Reviewed-on: https://go-review.googlesource.com/45612
Run-TryBot: Robert Griesemer <a6752097faebf1f02d80107d77a9be009089afe3@golang.org>
Reviewed-by: Matthew Dempsky <e56ac2c500064424afac424d4b5e53bd0570a731@google.com>

nawawi/go,Cofyc/go,cloudflare/go,cloudflare/go,CAFxX/go,akutz/go,polyverse-security/go,josharian/go,Cofyc/go,akutz/go,akutz/go,codestation/go,vsekhar/elastic-go,polyverse-security/go,nawawi/go,polyverse-security/go,golang/go,Cofyc/go,christopher-henderson/Go,akutz/go,CAFxX/go,polyverse-security/go,polyverse-security/go,polyverse-security/go,vsekhar/elastic-go,cloudflare/go,golang/go,nawawi/go,CAFxX/go,cloudflare/go,josharian/go,codestation/go,polyverse-security/go,vsekhar/elastic-go,cloudflare/go,akutz/go,CAFxX/go,akutz/go,Cofyc/go,nawawi/go,akutz/go,nawawi/go,josharian/go,codestation/go,akutz/go,vsekhar/elastic-go,nawawi/go,codestation/go,golang/go,josharian/go,CAFxX/go,josharian/go,Cofyc/go,cloudflare/go,Cofyc/go,polyverse-security/go,golang/go,golang/go,vsekhar/elastic-go,vsekhar/elastic-go,golang/go,josharian/go,CAFxX/go,golang/go,josharian/go,CAFxX/go,codestation/go,nawawi/go,josharian/go,vsekhar/elastic-go,vsekhar/elastic-go,codestation/go,codestation/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,Cofyc/go,cloudflare/go,codestation/go,Cofyc/go