rpath Issue with textproc/xmlada deeper than it appears

[John Marino <marino%netbsd.org@localhost>]

The textproc/xmlada package is embedding an rpath pointing at the wrkdir 
in it's libraries.  There's no problem for packages dependent on it to 
use because they can find the package without the rpath, and because 
"/usr/pkg/lib" is a fallback directory on the rpath.

I haven't been able to override this, so after talking with Adacore and 
looking at the compiler code, I've determined the gnat is not familiar 
with the concept of "destdir" and it's hardcoding the paths of the 
libraries at buildtime without possibility of (A) not using RPATH, (B) 
assigning user-specified rpath, or (C) use of $ORIGIN.

There was suggested a nasty hack which would have resulted in a fake 
rpath to /tmp, but it appears the real fix for this is to modify the 
behavior of the compiler.

Right now, I'm leaning to using $ORIGIN.  Does NetBSD properly support 
this?  DragonFly didn't as recently as 2.10 release, but I think that 
means 2.10 and below that any path using $ORIGIN would be equivalent to 
not be defined at all.

I'd also like to add the option to skip rpath altogether (there's a 
gnatlink switch for this), and then open a report to Adacore to 
hopefully inspire an upstream fix.

Luckily gcc 4.6.2 was just released, so I was about to update the 
compiler anyway.

John