Switch stack's Cabal build from Custom back to Simple

[Blaisorblade]

Split out of #2450. Right now (after #2223) we need a Custom build to possibly store in stack the list of dependencies it was built with. But @mgsloan explains that

Setup.hs files are generally gnarly for a variety of reasons - haskell/cabal#3065

EDIT: The idea would be to switch to Template Haskell for the job, ideas in
#2450 (comment) and pointers.

[mgsloan]

For the TH approach, I think it's gotta be runIO getStuffFromCabalDist. Stack already links against cabal, so it's not really an added dep.