This is another error related to using a newer version of texinfo than expected. It’s also another “wait for it to fail and then edit in the working directory” solution unless someone can provide a better option.
Once the build has failed with the following message:
grep.texi:291: @itemx must follow @item
open up $GUMSTIXTOP/tmp/work/x86_64-linux/grep-native-2.5.1-r2/grep-2.5.1/doc/grep.texi and delete lines 286 to 290 (inclusive). Side-effect: your generated documentation will no longer be perfect.