/usr/lib/pkgconfig/libmng.pc is in libmng-dev 2.0.2-0ubuntu3.
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=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include
Name: libmng
Description: Loads PNG/MNG/JNG files
Version: 2.0.2
Libs: -L${libdir} -lmng
Libs.private: -lz -lm -ljpeg -llcms2
Cflags: -I${includedir}
|