We don’t currently use it anywhere. It was used briefly for the
hb-fc-list tool, but this tool have not been built since 2015:
commit cd042fc8c4
Author: Behdad Esfahbod <behdad@behdad.org>
Date: Thu Jun 18 10:55:13 2015 -0700
[util] Disable hb-fc-list for now
Until I figure out what to do about the API, and finalize
the tool.
Khaled Hosny
Ebrahim Byagowi
Mathieu Duponchelle