Scripts such as /usr/bin/gapi2-fixup point to binaries in /usr/lib/gtk-sharp-2.0 which on 17.1 is /usr/lib64/gtk-sharp-2.0, so the scripts fail to execute. I used the patch in: https://bugs.gentoo.org/659422 to get it to even build.
2.12.45 builds fine, but still has the scripts pointing to /lib instead of /lib64. It looks like at least gapi-fixup, gapi-codegen, and gapi2-parser are affected. I have no idea if any of the slot 3 versions are affected in the same way.
This should also block bug 506276.
*** This bug has been marked as a duplicate of bug 645786 ***