/usr/lib/x86_64-linux-gnu/ is in libcairomm-1.0-dev 1.10.0-1ubuntu3.
This file is owned by root:root, with mode 0o755.
..
/usr/lib/x86_64-linux-gnu/libcairomm-1.0.a
/usr/lib/x86_64-linux-gnu/libcairomm-1.0.la
/usr/lib/x86_64-linux-gnu/cairomm-1.0/
/usr/lib/x86_64-linux-gnu/cairomm-1.0/include/
/usr/lib/x86_64-linux-gnu/cairomm-1.0/include/cairommconfig.h
/usr/lib/x86_64-linux-gnu/pkgconfig/
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-xlib-xrender-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-png-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-xlib-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-ps-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-svg-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-ft-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-1.0.pc
/usr/lib/x86_64-linux-gnu/pkgconfig/cairomm-pdf-1.0.pc
/usr/lib/x86_64-linux-gnu/libcairomm-1.0.so