/usr/lib/x86_64-linux-gnu/pkgconfig/cg3.pc is in libcg3-dev 1.0.0~r12254-1ubuntu3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 | prefix=/usr
exec_prefix=/usr
libdir=/usr/lib/x86_64-linux-gnu
includedir=/usr/include
Name: cg3
Description: CG-3 is a compiler and applicator for the third edition of the Constraint Grammar formalism.
Version: 1.0.0.12253
Libs: -L${libdir} -lcg3
Cflags: -I${includedir}/
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