How do I install header files not in GNUstep Header dirs?

[Sebastian Reitenbach]

Hi,

I want to install the header files below /usr/local/include, nevertheless 
what $GNUSTEP_HEADERS says where the files should go. In 
Makefiles/Instance/Shared/headers.make I haven't found a Variable that 
allows me to install to an arbitrary location, just like for the 
installation of TOOLS. Or do I have to overwrite the GNUSTEP_HEADERS 
variable before calling e.g. bundle.make or library.make, or would I then 
run into other problems?

cheers
Sebastian