TF-A: Add build option for Arm Feature Modifiers

This patch adds a new ARM_ARCH_FEATURE build option
to add support for compiler's feature modifiers.
It has the form '[no]feature+...' and defaults to
'none'. This option translates into compiler option
'-march=armvX[.Y]-a+[no]feature+...'.

Change-Id: I37742f270a898f5d6968e146cbcc04cbf53ef2ad
Signed-off-by: Alexei Fedorov <Alexei.Fedorov@arm.com>
3 files changed