Clean up after a build.

Usage: cabal clean [FLAGS]

Removes .hi, .o, preprocessed sources, etc.

Flags for clean:
 -h, --help                   # Show this help text
 -v[n], --verbose[=n]         # Control verbosity (n is 0--3, default
                                verbosity level is 1)
 --builddir=DIR               # The directory where Cabal puts generated build
                                files (default dist)
 --cabal-file=PATH            # use this Cabal file
 --keep-temp-files            # Keep temporary files.
 -s, --save-configure         # Do not remove the configuration file
                                (dist/setup-config) during cleaning. Saves
                                need to reconfigure.
