When installing a package to a different directory using `go build`,
`mv` cannot be used if the destination directory has the group sticky
bit set. Instead, `cp` should be used to make sure the destination
file has the correct permissions.
Fixes golang/go#18878.
Change-Id: I5423f559e7f84df080ed47816e19a22c6d00ab6d
Reviewed-on: https://go-review.googlesource.com/36797
Run-TryBot: Chris Manghane <cmang@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org>