/usr/lib/x86_64-linux-gnu/pkgconfig/ is in libopenscenegraph-3.4-dev 3.4.1+dfsg1-3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osg.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgAnimation.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgDB.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgFX.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgGA.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgManipulator.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgParticle.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgQt.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgShadow.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgSim.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgTerrain.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgText.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgUtil.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgViewer.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgVolume.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph-osgWidget.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/openscenegraph.pc