`juliadir` should probably not be cached during compile time

[KristofferC]

If you use another Julia installation that is compatible with the precompile file it will point to the wrong place:

julia> using Revise

julia> Sys.BINDIR
"/Users/kristoffercarlsson/Downloads/gitrepo/julia-1.10.4/bin"

# the Julia that Revise got compiled with:
julia> Revise.juliadir
"/Users/kristoffercarlsson/.julia/juliaup/julia-1.10.4+0.aarch64.apple.darwin14/share/julia"

[timholy]

Good thought. I'm tempted to fix this by requiring Julia 1.10 and using typed globals, rather than making a Ref which changes the type of this variable. It's internal, but I wouldn't be shocked if people are depending on it regardless (it has a docstring).