cmd/go: strip -fsanitize= flags when building cgo object Fixes issue 8788.
cmd/go: strip -fsanitize= flags when building cgo object
Fixes issue 8788.

LGTM=iant
R=iant
CC=golang-codereviews
https://codereview.appspot.com/142470043

tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go,tv42/old-go