/usr/lib/pkgconfig/GraphicsMagick.pc is in libgraphicsmagick1-dev 1.3.18-1ubuntu3.
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 11 | prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib
includedir=${prefix}/include/GraphicsMagick
Name: GraphicsMagick
Version: 1.3.18
Description: GraphicsMagick image processing library
Libs: -L${libdir} -lGraphicsMagick
Cflags: -I${includedir}
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