The bug was that withFile closes the handle afterwards, but the content
of the file was not read due to laziness. Using readFile avoids it.
This commit was sponsored by Nick Daly on Patreon.
The only thing lost is ./ghci
Speed: make fast used to take 20 seconds here, when rebuilding from
touching Command/Unused.hs. With cabal, it's 29 seconds.
This is so gratutious and pointless. It's a shame that everything we
learned about Unix portability and the importance of standards has been
thrown out the window by these guys.
