Add aarch64 native build support

Add support for Xilinx Zynq MPSoC to Linux config

This allows to boot the ACS-IR Linux kernel on the Xilinx ZCU102 board for
example.

Signed-off-by: Vincent Stehlé <vincent.stehle@arm.com>

Fixed build issue with 20.04 and updated IR read me

Signed-off-by: Jiss Jose <jiss.jose@arm.com>

Signed-off-by: edhay <edhaya.chandran@arm.com>

SystemReady Initial Check-in

Scripts and Instructions to build BSA and BBR ACS for SystemReady IR
README for SystemReady ES

Co-authored-by: Edhaya Chandran <edhaya.chandran@arm.com>
Co-authored-by: Jiss Jose <jiss.jose@arm.com>
Co-authored-by: Jeff Booher-Kaeding <jeff.booher-kaeding@arm.com>

Signed-off-by: Edhaya Chandran <edhaya.chandran@arm.com>
Signed-off-by: Gowtham Siddarth <gowtham.siddarth@arm.com>