scons: Fix 'CheckLinkFlag' so '-Werror' is not enabled

A small error in 'CheckLinkFlag' was resulting in `-Werror` being set
as a CXXFLAG after the function was run. This patch fixes this.

Change-Id: I786f81a4f94be0356573eb6d4673d04ee5aa844d
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/54863
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
1 file changed