> I am building a package that needs the value of a make variable from
> another package.  I am trying to do this with the following in my
> package Makefile:
> 
> XXX!=   cd ../../category/package && ${MAKE} show-var VARNAME=XXX
> 
> However, I am getting a variety of errors that seem to be related to
> the wrappers and buildlink handling.
> 
> Is there an established way to accomplish this?

A common way is to split out the variables and put them into some common 
mk file fragment (or Makefile.common). Then include that file as needed.

Look at the various Mkefile.common files for examples.