'setup makefile' generates a Makefile that performs the steps
necessary to compile the Haskell sources to object code.  This only
works for libraries, and only with GHC right now.

Instead of simply 'setup build', you can do this:

  $ ./setup makefile
  $ make
  $ ./setup build

where './setup makefile' does the preprocessing and generates a
Makefile tailored to the current package.  'make' will build all the
Haskell code to object files, and 'setup build' will build any C code
and the library archives.

The reason for all this is that you can say 'make -j' and get a
parallel build, or you can say

  make dist/build/Foo.o EXTRA_HC_OPTS=-keep-s-file

to compile a single file with extra options.