Local versions

Remarks:

1. The shim is hardcoded in ghcup currently. So if there is a bug, then we need to tell people to 'ghcup upgrade'. That could be a problem imo.
2. the shim does some additional work, I'm not sure if this will in fact slow down compilation processes? A cat call and a [ -f file ] check.
3. the local feature only works for the current directory (and only the current directory), there is no recursive upwards check performed, so if you are in a subdirectory of your project, it will not work

TODO:

• I think there was some logic checking for ghc etc being dangling symlinks, clean that up

Edge use case and it's not clear how this will interact with cabal. Closing for now.

closed