Is there already a mechanism with buildlink that allow to define certain
files that will be placed (or rather linked) in in the
.buildlink/include and .buildlink/lib directories so they are found
there for the configure and build process?
I could think of this being useful in two scenarios:
- systems which are missing essential headers or libraries
- people who want to use "private" versions of certain headers/libraries
instead of the system ones (of the same name) (maybe some commercial
math libs or some system libs optimized specifically for that system).

If it does not exist, it should be trivial to add variables called, say,
LOCALHEADERS and LOCALLIBS, which could be filled with a list of header
and libary files (full paths) to be symlinked into .buildlink/include
and .buildlink/lib. These variables could be set in mk.conf, if desired.

Such a  mechanism could, for example, be one means to solve the missing
regex lib problem on IRIX 5. It could also be used to have a private,
bug-free, copy of inttypes.h on that platform.  
  
Anyway, I would think with such a small measure one would offer a big
potential to pkgsrc for flexible local optimization.
-- 
Georg Schwarz    http://home.pages.de/~schwarz/
 georg.schwarz@freenet.de     +49 178 8545053