Build: allow setting of options for psa_arch_test

Don't override any of the variables that are passed to the psa_arch_test
buildsystem if they are already defined. Allows users to set -DSUITE etc
on the command-line if more fine-grained control of the psa_arch_test
build is required.

Change-Id: I141af5eae79d7f8ad797a0f46c0ba981e703ca80
Signed-off-by: Raef Coles <raef.coles@arm.com>
1 file changed