Getting pathname of BUILD_DEPENDS application

When compiling lang/swipl it is required to run.

	/usr/local/bin/uuid-config --cflags | --ldflags

... as part of deducing header / library placement of misc/ossp-uuid. This is all part of the cmake setup of lang/swipl, and currently I use an awful patch to hardcode something in the cmake file pre-make - but this file actually allows one to set a variable - $LibUUID_ROOT - to the path of uuid-config from the outside. I have successfully experimented with this, so I added:

	BUILD_DEPENDS=  uuid-config:misc/ossp-uuid

.. to the makefile. Now my question is: How do I properly get to the pathname of uuid-config?? In order to pass it to cmake somewhat like (pseudo):

	CMAKE_ARGS=     -DLibUUID_ROOT=${which uuid-config:sh:H}

... I have done loads of experiments and searched the webs to no avail.

	Thanks - N :o)