GNU builds with separate source and object trees

[Lloyd Parkes <lloyd%must-have-coffee.gen.nz@localhost>]

Hi,
Some GNU software (such as GCC) is designed to build with an object  
tree outside the source tree.

Is there any support for this in pkgsrc? At the moment I am using  
Makefile fragments like
        CONFIGURE_DIRS=         ../build
        CONFIGURE_SCRIPT=       ../${DISTNAME}/configure

but it would be nicer if I could just set a single variable to get  
all of the requisite build phases run in the right directory.

The latest GCC seems to get a bit confused when building the  
traditional way with shared source and object trees.

Cheers,
Lloyd