/usr/lib/x86_64-linux-gnu/pkgconfig/ is in libns3-dev 3.27+dfsg-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-antenna.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-aodv.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-applications.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-bridge.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-buildings.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-config-store.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-core.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-csma-layout.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-csma.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-dsdv.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-dsr.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-energy.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-fd-net-device.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-flow-monitor.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-internet-apps.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-internet.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-lr-wpan.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-lte.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-mesh.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-mobility.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-mpi.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-netanim.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-network.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-nix-vector-routing.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-olsr.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-point-to-point-layout.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-point-to-point.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-propagation.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-sixlowpan.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-spectrum.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-stats.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-tap-bridge.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-test.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-topology-read.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-traffic-control.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-uan.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-virtual-net-device.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-wave.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-wifi.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/libns3.27-wimax.pc