/usr/lib/x86_64-linux-gnu/pkgconfig/ is in libmrpt-dev 1:1.5.5-1.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-base.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-bayes.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-detectors.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-graphs.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-graphslam.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-gui.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-hmtslam.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-hwdrivers.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-kinematics.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-maps.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-nav.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-obs.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-opengl.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-reactivenav.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-scanmatching.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-slam.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-tfest.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-topography.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/mrpt-vision.pc