/usr/lib/x86_64-linux-gnu/pkgconfig/gdk-pixbuf-xlib-2.0.pc is in libgdk-pixbuf2.0-dev 2.31.1-2+deb8u7.
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=${prefix}/include
Name: GdkPixbuf Xlib
Description: GdkPixbuf rendering for Xlib
Version: 2.31.1
Requires: gobject-2.0,gmodule-no-export-2.0,gdk-pixbuf-2.0
Libs: -L${libdir} -lgdk_pixbuf_xlib-2.0
Cflags: -I${includedir}
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