Add data-dir to InstalledPackageInfo
Currently, the data directory of a package is not stored in the package database. This is fine for programs produced by GHC, where programs know the location of their own data files through the
Paths_packagename module, but it's not sufficient for programs that do not have direct access to the local filesystem.
Programs produced by GHCJS should be able to load their data files over HTTP. If GHCJS would know the
data-dir location of all packages, it could make the data files for all dependencies available when linking, and generate a
FilePath -> URI mapping table. The best it can currently do is making all files on the hard drive available.
I have a patch for this that I'll submit once I've figured out how Phabricator works ;)