staging: add ${datadir}/gtk-doc/html to the sysroot blacklist
When api-documentation is enabled the GNOME stack builds API documentation. As
${datadir} is in SYSROOT_DIRS this documentation is in the sysroot but is never
used, wasting time and space.
Add ${datadir}/gtk-doc/html to the blacklist so that the generated documentation
isn't in the sysroot. Note that we don't blacklist all of ${datadir}/gtk-doc
because gtk-doc itself installs files there which are needed to use gtk-doc.
Signed-off-by: Ross Burton <ross.burton@intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
