CL 89050043 only allows -ccflags for 'go test', this
CL really handles the flag like the other -??flags.
Many thanks to Dobrosław Żybort for pointing this out.
Fixes #7810 (again).

LGTM=iant, matrixik
R=golang-codereviews, iant, matrixik
CC=golang-codereviews
https://golang.org/cl/89230044