Pause is a legacy syscall not available on linux-arm64. Use ppoll with
all args as 0 to emulate - this is the way musl libc does Pause when the
pause syscall isn't available.

With the changes in syscall_linux* and regenerating zsyscall_linux*,
this calling Pause on linux-arm64 works and returns EINTR as expected.

Change-Id: I88236290313f18c742d826e759e86ff260a8b383
Reviewed-on: https://go-review.googlesource.com/22014Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>