haskell/cabal — pull request #1312 by 23Skidoo (2013-05-04 23:35:10+00:00)
Title: Use a non-default build dir when building add-source deps.

Fixes #1281.

I decided against using `.cabal-sandbox/dist/$PKGID` since we can have several add-source deps with a single `$PKGID`. Although that can probably be fixed by deleting the build dir when adding an add-source dep with an already-existing package id..