syscall: on linux-arm64, prefer prlimit to {g,s}etrlimit

Reportedly some Docker images accept the prlimit64 system call,
used by syscall.prlimit, but prohibit the getrlimit and setrlimit
system calls.

Fixes #38604

Change-Id: I91ff9370450b4869098cc8e335bbb7b863060508
Reviewed-on: https://go-review.googlesource.com/c/go/+/230339


Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>