- sed's `--unbuffered` argument does not exist. Simply dropping it isn't
  entirely ideal, but there doesn't seem to be any obvious alternative,
  and I doubt it'll result in any significant regressions.
- For reasons unknown to me, `tempfile` seems to now be failing due to
  the test name containing a slash. I'm not sure if this is an area
  where some differing behavior in ash vs bash resulted in passing a
  value with a slash, but the easiest workaround is just to replace them
  with underscores.
  - On that note, I also migrated to mktemp, since tempfile has been
    deprecated for a long time and was recently removed, plus making the
    switch was incredibly simple.

https://phabricator.apertis.org/T8423



Signed-off-by: Ryan Gonzalez <ryan.gonzalez@collabora.com>