I don't think the existing logic is correct, as the comment says, our internal
state is only matched if we *actually* wrote out the file. But if we ran into an
error, it doesn't match, does it?
The lines of code I commented on in #10254 were meant to serve only as examples
of the changes I was requesting, not the only instances.
Also just use `Mode::from_bits_truncate()` instead of unsafe or unwrapping since
we know the modes are correct.
This was previously limited to Linux predicated on the existence
of certain headers, but Rust just exposes those functions unconditionally. So
remove the check and just perform the mtime hack on Linux and Android.
