Getting the version of an installed dependency?

[Paul Ripke <stix%stix.id.au@localhost>]

I'm cleaning up a bunch of packages to commit, and have run into
something I don't have a clean solution for:

wip/nlopt optionally installs file paths containing the version string
from the installed math/octave... currently I'm storing OCTAVE_VERSION
in nlopt's options.mk, but this is rather fragile. Is there a common
solution? Export OCTAVE_VERSION from octave's buildlink3.mk?

-- 
Paul Ripke
"Great minds discuss ideas, average minds discuss events, small minds
 discuss people."
-- Disputed: Often attributed to Eleanor Roosevelt. 1948.