Compile the same package with respect to several sets of flag states

(Imported from [Trac #837](http://hackage.haskell.org/trac/hackage/ticket/837), reported by lemming on 2011-04-24)

Currently I have configured my cabal with --enable-library-profiling, --enable-shared, what leads to problems with the GHC-7.0.\* archives that do not contain shared objects for profiling. Actually, I do not need them, but I cannot tell Cabal to omit shared objects for profiling. If I use --enable-library-profiling and --enable-shared, then all combinations of {static, dynamic} x {non-profiling, profiling} are generated.

Instead of enabling two variants by each of those 'enable' options and then generating code for all possible combinations, I would find it more useful to define sets of flags and compile modules with respect to all of these flag sets. E.g. I could write something like the following to ~/.cabal/config:

flagset: dyn

   shared: True

   optimization: True

flagset: p

   shared: False

   profiling: True

   optimization: True

   rts-options: True

flagset: dbg

   flags: debug

   optimization: True

For every module A this should generate A_dyn.o, A_p.o, A_dbg.o.

I do not know whether this problem can be solved in Cabal alone, or whether it also needs adaption of GHC.

See also:

• #600
  
• [http://hackage.haskell.org/trac/ghc/ticket/5021](http://hackage.haskell.org/trac/ghc/ticket/5021)