point to the wiki for "Setting up your system for building GHC" (#5874)
point to the wiki for "Setting up your system for building GHC" (#5874)

MERGED from commit 95d2e12cbee185dd78a66e4cd44d6915519f1fa9

ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix,ilyasergey/GHC-XAppFix