Untested, on FreeBSD but enough to fix the listed build errors.
Seems that System.Posix.Files must have used to export this stuff and it
was split.
This commit was sponsored by Peter on Patreon.
Switch to Data.Map.Strict everywhere that used it.
There are still lots of lazy maps in git-annex. I think switching these
is safe. The risk is that there might be a map that is used in a way
that relies on the values not being evaluated to WHNF, and switching to
strict might result in bad performance or memory use. So, I have not
switched everything.
