Alp Mestanogullari authored Aug 01, 2019 and Marge Bot committed Aug 02, 2019

This fixes #17003, where a user directly asked for the 'docs-haddock' target
without building a complete stage 2 GHC first. Since haddock only depends on
lib:ghc, the stage 2 GHC executable wasn't built, and neither were the
settings, platformConstants, llvm-passes and llvm-targets files, since they
are declared to be dependencies of exe:ghc.

This makes sense in general since all GHC API users (haddock is one) will likely
want those files to be there.