[Haskell-cafe] ghcup and XDG support

The ghcup-hs README contains a rather nebulous remark ( https://github.com/haskell/ghcup-hs#xdg-support): Note that ghcup makes some assumptions about structure of files in XDG_BIN_HOME. So if you have other tools installing e.g. stack/cabal/ghc into it, this will likely clash. In that case consider disabling XDG support. Which assumptions does it make? What will clash and when? I very much prefer XDG-style installations, but I don't want to find out the downsides the hard way afterwards... ;-) Cheers, S.