syscall_emul: implement arm openat

This is especially important because the Ubuntu 18.04 packaged
arm-linux-gnueabihf-gcc uses the system call on the program initialization,
which leads all programs to fail with:

fatal: syscall openat (#322) unimplemented.

Change-Id: I5596162ad19644df7b6d21f2a46acc07030001ae
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/13004
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
1 file changed