runtime: use Android O friendly faccessat syscall on linux/amd64

runtime: use Android O friendly faccessat syscall on linux/amd64

The Android O seccomp policy disallows the access syscall on amd64, see
https://android.googlesource.com/platform/bionic/+/android-4.2.2_r1.2/libc/SYSCALLS.TXT

Use the faccessat syscall with AT_FDCWD instead to achieve the same
behavior.

Updates #24403

Change-Id: I9db847c1c0f33987a3479b3f96e721fb9588cde2
Reviewed-on: https://go-review.googlesource.com/100877
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>