fix 'clean' bug on windows caused by leaked Handle.
fix 'clean' bug on windows caused by leaked Handle.

Using readFile to read dist/setup-config keeps the Handle open when we try to delete the file, causing an error. 
So we instead read the file strictly and close the Handle early.

20080318161237-cd449-6d499624f7e72219411b4f534859f67c64e744c3.gz

dcreager/cabal,dcreager/cabal