cmd/go: fix TestFFLAGS for Fortran compilers that accept unknown options
The test assumed that passing an unknown option to the Fortran
compiler would cause the compiler to fail. Unfortunately it appears
that some succeed. It's irrelevant to the actual test, which is
verifying that the flag was indeed passed.
Fixes #19080.
Change-Id: Ib9e89447a2104e4742f4b98938373fc2522772aa
Reviewed-on: https://go-review.googlesource.com/37658
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Alex Brainman <alex.brainman@gmail.com>