Build: Support Armclang in build split

Add and export a NS toolchain file example of Armclang.
Use Armclang NS scatter file when NS is built with Armclang.

Change-Id: Ic4d30ebf3089efce6427b4ff329c68cee97f8ade
Signed-off-by: David Hu <david.hu@arm.com>
3 files changed