refering to this problem
http://help.gnomedesktop.org/forums/viewtopic.php?t=191

during 'make install' on various gnome package
some ppl including me faced cannot stat ./html/index.sgml (missing)
(index.sgml might not generated)

the problem arise when there is no sgml tool or similar installed on the
machine.

but, while compiling gtk-doc, it's just say it need openjade
& then while compiling openjade, it didnt ask for sgmltools

so i would like to suggest,
gtk-doc check whther the openjade has sgml tool support OR
check whther sgml tool installed.