syscall: Faccessat: use faccessat2 on linux

syscall: Faccessat: use faccessat2 on linux

Linux kernel 5.8 added the faccessat2 syscall taking a flags argument.
Attempt to use it in Faccessat and fall back to the existing
implementation mimicking glibc faccessat.

Do not export the new syscall value so we keep syscall API intact.

Part of this commit is generated by:

	GOOS=linux ./mkall.sh -syscalls zsyscall_linux_*.go

This is similar to [1] amended by [2]. Required for [3].

[1] https://go-review.googlesource.com/c/sys/+/246537
[2] https://go-review.googlesource.com/c/sys/+/246817
[3] https://go-review.googlesource.com/c/go/+/414824

Co-authored-by: Tobias Klauser <tklauser@distanz.ch>
Change-Id: Ib7fe5ba853c15d92e869df9a16b56b79b96e43a6
Reviewed-on: https://go-review.googlesource.com/c/go/+/416115
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Reviewed-by: Bryan Mills <bcmills@google.com>