/usr/lib/x86_64-linux-gnu/pkgconfig/ is in libgstreamer-plugins-base1.0-dev 1.2.3-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-rtsp-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-tag-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-audio-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-app-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-sdp-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-pbutils-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-allocators-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-rtp-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-fft-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-video-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-plugins-base-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gstreamer-riff-1.0.pc