scons: Fix --with-ubsan/asan compilation flags

SConstruct was using an undefined env variable; this patch uses the main
Environment variable.

Change-Id: I30ab6b4bbfa6d9a71a30fb33406a799bfb476821
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/10181
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>
1 file changed