Fix hijacking for ARM/ARM64/x86 on Unix (#20042)

Fix hijacking for ARM/ARM64/x86 on Unix (#20042)

* Fix hijacking for ARM/ARM64/x86 on Unix

We were not checking the case when we have interrupted a thread inside
of a function epilog for other architectures than amd64. When such an
interruption happens, GS cookie check in a stack walking has failed,
since we are unable to decode GS cookie location when the IP is in
epilog.
This fix implements IsIPInEpilog for all architectures and makes the
check unconditional.

Change-Id: I365be79d6b43ec900084bf2ec031b3555917f8e0