We install GHC using the binary release directly because installation of
GHC via ghcup or via stack in the formula context is not reliable.

Specifially the GHC installation with ghcup or stack
fails *sometimes* (with about 1/5 frequency) when trying to create a
temporary directory within the temporary HOME directory used by the
formula build.

The GHC installer works reliably when invoked directly from the bindist

In particular we were not specifying a git ref for the stable version
the git ref of the `main` branch was always used. This is now fixed by
specifying the `revision` field on the juvix git URL.