We test against 9.2.7 now, so we should make our stack config reflect
that—plus, it's more convenient for users, since one is more likely to
already have the latest minor version of GHC installed.
Related: 67064ddd9264bbe39d6fa88fd8336086817dd0db
This was temporarily disabled in 229d52ff07 and 086db3123b because we
couldn't keep xmonad-contrib backwards compatible with xmonad 0.15 any
more, but xmonad 0.17.0 is out now and we can try to stay compatible for
a while.
Building xmonad-contrib benefits greatly from compiling modules in
parallel. Vanessa McHale suggested setting ghc-options in
xmonad-contrib.cabal in #431, but that's bad practice—these options
should be set by the user/environment where it's being built, not
selfishly hardcoded for specific package. In stack.yaml and
cabal.haskell-ci, we know for sure that xmonad-contrib is the terminal
(leaf) library, so we can set it there and speed up builds in our CI and
also for anyone who uses our stack.yaml (not that anyone should).
Closes: https://github.com/xmonad/xmonad-contrib/pull/431
