Pass other-modules to `ghc --make` for exe components
Pass other-modules to `ghc --make` for exe components

`gbuildSources` was introduced by a refactoring in
382143aa7322605d1a9f0480e383490e186c7ea0 but there
doesn't appear to be a good reason why the modules are
only passed for a non-haskell main module.

So this patch consistently passes `other-modules` to
`ghc --make` for both variants of executables.

Addresses part of #4528

themoritz/cabal,themoritz/cabal,mydaum/cabal,mydaum/cabal,themoritz/cabal