Fixes out of date glib tools throwing errors.

/usr/bin/glib-genmarshal --prefix _gdk_pixbuf_marshal --output gdk-pixbuf/gdk-pixbuf-marshal.h --pragma-once --header ../gdk-pixbuf/gdk-pixbuf-marshal.list
FAILED: gdk-pixbuf/gdk-pixbuf-marshal.h
/usr/bin/glib-genmarshal --prefix _gdk_pixbuf_marshal --output gdk-pixbuf/gdk-pixbuf-marshal.h --pragma-once --header ../gdk-pixbuf/gdk-pixbuf-marshal.list

(process:12337): GLib-Genmarshal-WARNING **: failed to open "--output": No such file or directory

(process:12337): GLib-Genmarshal-WARNING **: failed to open "gdk-pixbuf/gdk-pixbuf-marshal.h": No such file or directory

(process:12337): GLib-Genmarshal-WARNING **: failed to open "--pragma-once": No such file or directory

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