With the old code, if the currentErrno hadn't changed, but was in
fact re-assigned more recently than the local errno was, then we
would wind up incorrectly return the local value instead of the
system value. This was the cause of the build mimeset not working
properly when run in recursive mode on Haiku.
So, instead, create a wrapper struct to make assignment of the
local errno always pass through to the system one, so they never
get out of sync in the first place.
Augustin Cavalier
744616c074