...
ocamlopt.opt -w s -c gutf8.ml
+ gcc -fPIC -Os -std=gnu99 -O2 -fno-strict-aliasing -fwrapv -Wall -D_FILE_OFFSET_BITS=64 -D_REENTRANT -fPIC -c -DG_DISABLE_ASSERT -DG_DISABLE_CAST_CHECKS -fno-unwind-tables -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/atk-1.0 -I/usr/include/librsvg-2.0 -I/usr/include/gtkspell-2.0 -I/usr/include/gtksourceview-2.0 -pthread -I/usr/include/libxml2 -imacros ml_domain.h -O -I'/usr/lib/ocaml' 'ml_gtkspell.c'
+ gcc -fPIC -Os -std=gnu99 -O2 -fno-strict-aliasing -fwrapv -Wall -D_FILE_OFFSET_BITS=64 -D_REENTRANT -fPIC -c -DG_DISABLE_ASSERT -DG_DISABLE_CAST_CHECKS -fno-unwind-tables -I/usr/include/gtk-2.0 -I/usr/lib/gtk-2.0/include -I/usr/include/pango-1.0 -I/usr/include/glib-2.0 -I/usr/lib/glib-2.0/include -I/usr/include/cairo -I/usr/include/pixman-1 -I/usr/include/freetype2 -I/usr/include/libpng16 -I/usr/include/harfbuzz -I/usr/include/gdk-pixbuf-2.0 -I/usr/include/atk-1.0 -I/usr/include/librsvg-2.0 -I/usr/include/gtkspell-2.0 -I/usr/include/gtksourceview-2.0 -pthread -I/usr/include/libxml2 -imacros ml_domain.h -O -I'/usr/lib/ocaml' 'ml_rsvg.c'
ocamlc.opt -w s-3+52 -warn-error A-52 -c gpointer.ml
ocamlc.opt -w s-3+52 -warn-error A-52 -c gutf8.ml
ocamlc.opt -w s-3+52 -warn-error A-52 -c gobject.mli
File "gtkThInit.ml", line 27, characters 13-28:
Error: Unbound module GtkThread
make[1]: *** [Makefile:192: gtkThInit.cmo] Error 2