Implement missing posix utils Bug: angleproject:2923 Change-Id: I35fee6303f07c7b3a931f876a8d9d4ba54c91630 Reviewed-on: https://chromium-review.googlesource.com/c/1315607 Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>