cabal new-run silliness

[yav]

I have a cabal package that defines a library and executable. Not surprisingly, they have the same name. Here is what happens when I try to use cabal new-run with it:

$ cabal new-run cryptol
cabal: Ambiguous target 'cryptol'. It could be:
exe:cryptol (component)
lib:cryptol (component)

It doesn't really make sense to run a library (and Cabal knows that, as it reports an error if you try to do so), so new-run should only consider the executable targets and filter out the rest.

[23Skidoo]

/cc @fgaz

[fgaz]

Duplicate of #4676