Supporting native OS X Qt

[Edgar Fuß <ef%math.uni-bonn.de@localhost>]

Has anyone tackled supporting native Qt on Mac OS X?

When, on Mac OS X pkgsrc, I build a package depending on Qt, I get the X11
version of Qt built, which is most probably not what I want because there is
a native Mac OS X version of Qt.
Additionally, since there is a binary package (not in the pkgsrc, but in the
OS X sense) of Qt, I may have that installed on my machine. This can probably
be compared to having a native X11 installed.
If I don't have the TrollTech binary package installed, I probably want the
native Qt built from sources.

Any suggestions how to handle this? How do I make a package depend on Qt,
but not explicitly on, say, qt4-libs? How can I make a pseudo-package provide
qt4-libs on a machine with the TrollTech binary installed?
I suppose there is prior art in pkgsrc for such a situation, as various other
functionality (X11, perl) may or may not be provided by the underlying platform.

Thanks for any suggestions.