haskell: use buildlink3 files?

[Thomas Klausner <wiz%NetBSD.org@localhost>]

Hi!

While fixing some problems with non-building hs-* packages I noted
that I can add DEPENDS to get the dependencies installed and usable by
the Haskell compiler.

However, most hs-* packages provide a buildlink3.mk file.

For Python, we decided that since the compiler is not involved, we
want to avoid using buildlink3.mk and instead use plain DEPENDS. I
think this also gives a parsing speedup because less files are opened.

Do we want to decide the same for Haskell, or can buildlink be
extended to work as intended for Haskell packages as well? (I.e., that
hs-* packages that are not buildlinked will not be found by the
Haskell compiler.)

If yes, is anyone willing to work on this?

Cheers,
 Thomas