The PGDG-mirrored GIS libraries percona-postgis builds against (GEOS,
PROJ, libgeotiff, librttopo, libspatialite, GDAL, SFCGAL). GDAL links
against the libpq of the pinned PG major (macros.yaml PG_MAJOR_VERSION),
so this project paths to ppg:staging:<that major>; ppg:common:deps cannot,
because every ppg:staging:<V> paths to ppg:common:deps (circular).
Consumed by ppg:staging:<V> only through obs/_aggregate packages
(root/ppg/staging/_shared/<pkg>/obs/_aggregate), hence never published
from here.