Spack Install No Longer Works

The following error pops up when trying to spack install this repo:

```
❯ spack install
==> Error: failed to concretize `enzyme`, `gmake`, `cmake` for the following reasons:
1. Only external, or concrete, compilers are allowed for the fortran language. You could consider setting `concretizer:unify` to `when_possible` or `false` to allow multiple versions of some packages.
```

Even after making the recommended changes to the spack.yaml, a similar error pops up

```
❯ spack install
==> Compilers have been configured automatically from PATH inspection
==> Starting concretization pool with 3 processes
==> Error: failed to concretize `enzyme` for the following reasons:
1. Only external, or concrete, compilers are allowed for the fortran language
```

This happens on WSL Ubuntu.

Spack is the only cross platform option (building from source with CMake seems intractable) , so having this option would be key for any scientific use cases.