install-dirs
  prefix: cabal
  bindir: $prefix/bin
  libdir: $prefix/lib
  libsubdir: $pkgid/$compiler
  libexecdir: $prefix/libexec
  datadir: $prefix/share
  datasubdir: $pkgid
  docdir: $datadir/doc/$pkgid
  htmldir: $docdir/html
  haddockdir: $htmldir