It's possible for one of the ldflags to cause the compiler driver to
use a different linker than the default, so we need to make sure that
the flag is supported by whichever linker is specified.

Fixes #27110.

Change-Id: Ic0c51b886e34344d324e68cbf6673b168c14992f
Reviewed-on: https://go-review.googlesource.com/130316
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>