Loading a main-is module in emacs should run `cabal repl <target>` when there are multiple cabal stanzas

[amcphail]

This might be a duplicate of #1840.

I have a cabal file with a library stanza and two executable stanzas. When I attempt to load (C-c C-l) the main-is: Main.hs file I get module not found errors because I assume cabal repl is looking at the library stanza which does not have the same build-depends as the executable stanza.

If I customize-variable haskell-process-args-cabal-repl to include the executable stanza name then loading the file works. This is annoying though, as I want to alternate between executable modules and not customize-variable every time.