arm64 linuxulator: arm64 linux64 sysvec

[emaste]

Summary

Combined with D15832 this provides a minimal arm64 linuxulator implementation capable of executing Linux 'hello world' binaries

[emaste]

Minor tidyup

[andrew]

sys/arm64/linux/linux_sysvec.c

138 ↗

(On Diff #44041)

I think you can extract the needed buts from cpu_fetch_syscall_args. We need to memcpy the args, set the code from x8, then set callp as in amd64.

148 ↗

(On Diff #44041)

We need to update cpu_set_syscall_retval to us SV_ABI_ERRNO in the default case to translate Linux errno values.