I have no test case for this, but there is one report on the mailing list
(https://groups.google.com/d/msg/golang-dev/sDg-t1_DPw0/-AJmLxgPBQAJ)
in which waitid running on MIPS returns EFAULT.

Change-Id: I79bde63c7427eefc1f2925d78d97cc9cf2fffde3
Reviewed-on: https://go-review.googlesource.com/46511
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>