migrate response file support to process directly?

Given that lots of programs now support response files, and that we're teaching haskell tools one-by-one to support response files, do we want to put support for calling programs with response files into the process library directly? I'd suggest a new external lib, but the things we want to provide this to are all rather low in the dep-tree themselves -- i.e., ghc itself, cabal, hsc2hs, etc.

I'd think we could just e.g. port over http://hackage.haskell.org/package/Cabal-2.4.1.0/docs/Distribution-Simple-Program-ResponseFile.html

Review the process library and the linked Cabal Distribution-Simple-Program-ResponseFile module first. Determine whether response-file support belongs directly in process or an external library, and document the proposed scope and affected callers such as ghc, cabal, and hsc2hs.

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