feat(toolchains/aarch64): use -march=armv9.2 option

This patch sets "-march" option for aarch64 builds
from "armv9.2-a" to "armv8.5-a" depending on version
supported by C compiler.

Change-Id: Ifbd211694045e12ae482af1815413d2b4ef6762a
Signed-off-by: AlexeiFedorov <Alexei.Fedorov@arm.com>
3 files changed