internal/syscall/unix, os: add and use Waitid syscall wrapper on linux
Instead of open-coding the waitid syscall wrapper add it to
internal/syscall/unix. As the syscall is currently only used on Linux,
switch the implementation in os.(*Process).blockUntilWaitable to use the
128-byte unix.SiginfoChild type instead of a plain 128-byte buffer.
Also use ignoringEINTR for the waitid calls instead of open-coding it.
Change-Id: I8dc47e361faa1f5e912d5de021f119c91c9f12f5
Reviewed-on: https://go-review.googlesource.com/c/go/+/629655 Reviewed-by: Dmitri Shuralyov <dmitshur@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Tobias Klauser <tobias.klauser@gmail.com>