build: Fix dependency of output binaries on linker script

A linker script (scatter file) modification does not cause the
output binaries (tfm_s.axf, tfm_ns.axf) rebuild

Signed-off-by: Anton Komlev <anton.komlev@arm.com>
Change-Id: I3c4d1923ba166053e26835724a306cdf09705aec
3 files changed