/usr/lib/x86_64-linux-gnu/pkgconfig/glu.pc is in libglu1-mesa-dev 9.0.0-2.1.
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 11 | prefix=/usr
exec_prefix=${prefix}
libdir=${prefix}/lib/x86_64-linux-gnu
includedir=${prefix}/include
Name: glu
Description: Mesa OpenGL Utility library
Requires: gl
Version: 9.0.0
Libs: -L${libdir} -lGLU
Libs.private: -lm
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