Support for tempfile crate on UNIX hosts

[Jefffrey]

Reviving old PR: #2720

Attempted to apply the changes as suggested by #2720 (comment)

To fix tempfile to work for UNIX targets only and fall back to previous behaviour of only supporting default mode for Windows targets

[rustbot]

There are merge commits (commits with multiple parents) in your changes. We have a no merge policy so these commits will need to be removed for this pull request to be merged.

You can start a rebase with the following commands:

$ # rebase
$ git rebase -i master
$ # delete any merge commits in the editor that appears
$ git push --force-with-lease

The following commits are merge commits:

• cf4e094

[RalfJung]

Looks good, thanks!

Could you please squash this into a single commit? (Or two commits, one by Pointerbender and one by you)

[Jefffrey]

Squashed to single commit

[RalfJung]

Thanks. :)

@bors r+

[bors]

📌 Commit 06add70 has been approved by RalfJung

It is now in the queue for this repository.

[bors]

⌛ Testing commit 06add70 with merge fe1a722...

[bors]

☀️ Test successful - checks-actions
Approved by: RalfJung
Pushing fe1a722 to master...