scons: Get rid of a flag which makes Werror optional.

This flag wasn't being used. Also move the Werror code to the
SConstruct now that it's being applied universally.

Change-Id: I18b00d4b41bc1add9271ca299c020c14970a6926
Reviewed-on: https://gem5-review.googlesource.com/5982
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
2 files changed