sys_util: Add conversion from errno io::Error.
sys_util: Add conversion from errno io::Error.

Change-Id: Ia49aa8eac1dedbc4e3f6277120bf332404e8b818
Reviewed-on: https://chromium-review.googlesource.com/509918
Commit-Ready: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Tested-by: Dylan Reid <c791bfe44996c1eed9c7149a0c5f12a86d58eb85@chromium.org>
Reviewed-by: Zach Reizner <3374927928a53d04457674c546bd4de57c2044ec@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm