This change should make it less confusing where utility code comes from.
Having it in two places made sense when we were debating whether to publish
Sandbox2 separately, but not any longer.
Follow-up changes will move `sandbox2/util.h` and rename the remaining
`sandbox2/util` folder.
PiperOrigin-RevId: 351601640
Change-Id: I6256845261f610e590c25e2c59851cc51da2d778
Sending -1 as fd will fail and take forkserver down.
This should not happen normally so turned it into a check.
PiperOrigin-RevId: 285391908
Change-Id: Idbb05004c36cb0be57be1bd26df1c57cecfb0019
