/usr/lib/x86_64-linux-gnu/ is in libfsoframework-dev 0.12.0-4.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/pkgconfig/
/usr/lib/x86_64-linux-gnu/pkgconfig/fsoframework-2.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/fsoresource-2.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/gsm0710mux-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/fsotransport-2.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/fsotest-2.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/fsobasics-2.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/fsosystem-2.0.pc
/usr/lib/x86_64-linux-gnu/libfsoframework.so
/usr/lib/x86_64-linux-gnu/libfsobasics.so
/usr/lib/x86_64-linux-gnu/libgsm0710mux.so
/usr/lib/x86_64-linux-gnu/libfsotransport.so
/usr/lib/x86_64-linux-gnu/libfsosystem.so
/usr/lib/x86_64-linux-gnu/libfsoresource.so
/usr/lib/x86_64-linux-gnu/libfsotest.so