One-component configure, fixes #2802.
Described in: https://github.com/ghc-proposals/ghc-proposals/pull/4 ./Setup configure now takes an argument to specify a specific component name that should solely be configured. Most of the gyrations in Configure are all about making it so that we can feed in internal dependencies via --dependency. I dropped the package name match sanity check to handle convenience library package name munging. Consider an internal library named 'q' in package 'p'. When we install it to the package database, we munged the package name into 'z-p-z-q', so that it doesn't conflict with the actual package named 'q'. Now consider when we feed it in with --dependency q=p-0.1-hash-q. Previously, Cabal checked that the 'q' in --dependency matched the package name in the database... which it doesn't. So I dropped the check. I also had to make register/copy unconditionally install internal libraries; otherwise you can't refer to them from later builds. Also a miscellaneous refactor: convenience libraries are printed with a "header" stanza now (not really a stanza header). Signed-off-by: Edward Z. Yang <firstname.lastname@example.org>