Multi-repl doesn't pass GHC options in an idiomatic way

The multi-repl code does some ad-hoc things to come up with "extra" arguments for things like `-working-dir`, `-rexported-modules` etc

Instead, the `GhcOptions` data type should be extended with these options, and then rendering implemented alongside the other options. 

This is just a code quality improvement, no functional change is expected.

