Supporting accelerator builds for `dev.eessi.io`

[ocaisa]

What we want to support for developers is probably:

/path/to/dev.eessi.io/accel/modules:/path/to/dev.eessi.io/modules:/path/to/software.eessi.io/accel/modules:/path/to/software.eessi.io/modules

But the installation script is currently not configured to support this