Out of curious, I also git clone the openembedded recipes. After comparison, I find Intel's clanton distribution has included a meta-oe folder, which pretty much has duplicated the recipes in openembedded. Specifically, as Alex pointed out, the ruby recipe is included in meta-oe. (but I haven't tried to compile it.)
For people playing Linux on Galileo, eventually you will encounter a package you needed but can not find a recipe anywhere. More fundamental question seems to be on how to create a new recipe from scratch, or at least compile a package on the sideline and then merge into yoctco image. But that is totally another question. In the mean time, compile a missing package on Galileo directly seem to be a more straight way to go.