The build system of gobject-introspection-0.6.7 was overhauled, thus the patch gobject-introspection-0.6.2-gir.patch doesn't apply -- and after testing on my system (amd64) it was not necessary. Using libtool-2.2.6b even the sed changes in the ebuild with regard to libtool were not needed (however, I don't know if these lines are needed for other libtool versions - it builds with and without the removal of the m4 macros and the sed changes).
Commit reverted. The package needs a few more fixes too.