Revert "Extend Haskell generic builder to use new --ipid flag."

This reverts commit ec8b8161. The change told
the Cabal build system to use the hash-part of $out as the internal identifier
for the library it's building (rather than generating such an ID itself). While
a good idea in theory, this choice had an unfortunate side-effect: When Cabal
links libraries X, Y, and Z into an executable, then the generated binary
contains their respective IDs. Now, Nix finds those strings and treats them as
an indication that there is a *run-time dependency* on the corresponding store
paths. This means that the generated executable will always depend on the store
paths of all the Haskell libraries that went into it, even when linked
statically.