Build: allow multiple link time dependencies

Append to the `LINK_DEPENDS` property in `target_add_scatter_file` to
allow multiple dependencies for linking a target.

Change-Id: I294258fb5c5a799691f3ff340ebd9ee183809bbf
Signed-off-by: Anubhav Raina <anubhav.raina@arm.com>
3 files changed