/usr/lib/pkgconfig/ is in libns3-dev 3.17+dfsg-1build1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/pkgconfig/libns3.17-bridge.pc
/usr/lib/pkgconfig/libns3.17-dsr.pc
/usr/lib/pkgconfig/libns3.17-wimax.pc
/usr/lib/pkgconfig/libns3.17-mpi.pc
/usr/lib/pkgconfig/libns3.17-tools.pc
/usr/lib/pkgconfig/libns3.17-energy.pc
/usr/lib/pkgconfig/libns3.17-dsdv.pc
/usr/lib/pkgconfig/libns3.17-mesh.pc
/usr/lib/pkgconfig/libns3.17-point-to-point.pc
/usr/lib/pkgconfig/libns3.17-spectrum.pc
/usr/lib/pkgconfig/libns3.17-test.pc
/usr/lib/pkgconfig/libns3.17-virtual-net-device.pc
/usr/lib/pkgconfig/libns3.17-netanim.pc
/usr/lib/pkgconfig/libns3.17-fd-net-device.pc
/usr/lib/pkgconfig/libns3.17-uan.pc
/usr/lib/pkgconfig/libns3.17-topology-read.pc
/usr/lib/pkgconfig/libns3.17-tap-bridge.pc
/usr/lib/pkgconfig/libns3.17-applications.pc
/usr/lib/pkgconfig/libns3.17-wifi.pc
/usr/lib/pkgconfig/libns3.17-aodv.pc
/usr/lib/pkgconfig/libns3.17-csma.pc
/usr/lib/pkgconfig/libns3.17-lte.pc
/usr/lib/pkgconfig/libns3.17-emu.pc
/usr/lib/pkgconfig/libns3.17-mobility.pc
/usr/lib/pkgconfig/libns3.17-nix-vector-routing.pc
/usr/lib/pkgconfig/libns3.17-visualizer.pc
/usr/lib/pkgconfig/libns3.17-point-to-point-layout.pc
/usr/lib/pkgconfig/libns3.17-buildings.pc
/usr/lib/pkgconfig/libns3.17-flow-monitor.pc
/usr/lib/pkgconfig/libns3.17-network.pc
/usr/lib/pkgconfig/libns3.17-config-store.pc
/usr/lib/pkgconfig/libns3.17-propagation.pc
/usr/lib/pkgconfig/libns3.17-core.pc
/usr/lib/pkgconfig/libns3.17-internet.pc
/usr/lib/pkgconfig/libns3.17-csma-layout.pc
/usr/lib/pkgconfig/libns3.17-stats.pc
/usr/lib/pkgconfig/libns3.17-olsr.pc
/usr/lib/pkgconfig/libns3.17-antenna.pc