The existing ptrace wrapper accepts pointer argument as an uintptr which
often points to the memory allocated in Go. This violates unsafe.Pointer safety
rules.

Fixes #58387

Change-Id: Iab12122c495953f94ea00c2a61654a818a464205
Reviewed-on: https://go-review.googlesource.com/c/go/+/470299


TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Dmitri Goutnik <dgoutnik@gmail.com>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Dmitri Goutnik <dgoutnik@gmail.com>