/usr/lib/x86_64-linux-gnu/pkgconfig/libsidplayfp.pc is in libsidplayfp-dev 1.6.0-1.
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 | prefix=/usr
exec_prefix=${prefix}
libdir=${prefix}/lib/x86_64-linux-gnu
includedir=${prefix}/include
Name: libsidplayfp
Description: C64 cycle exact stereo sidplayer library.
Version: 1.6.0
Libs: -L${libdir} -lsidplayfp
Cflags: -I${includedir}
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