[pacman-dev] [PATCH] Use a bashism instead of mktemp's --tmpdir option.

I discovered that bacman and updpkgsums use --tmpdir while playing around in a busybox environment with pacman installed, as updpkgsums did not work. I've tested the attached patch in both that environment against pacman 4.2.1, and against a git checkout on a normal Arch system; both appear to work, but I may have misunderstood the reasoning behind using --tmpdir.