* /apps/gentoo/usr/bin/rdoc21 * /apps/gentoo/usr/bin/ri21
Could you please provide all the output?
Created attachment 464854 [details] build.log
Created attachment 464856 [details] build.log
Created attachment 464858 [details] build.log My bad!
Looking at the output this on prefix? I'm wondering about the different paths in the portage output, where one mentions a prefix of /apps/gentoo and the other does not. In any case /usr/bin/rdoc21 should be installed only by dev-ruby/rdoc. I'm not aware of any bugs related to this for ruby 2.1.10. Perhaps the best course of action would be to re-emerge ruby 2.1.10 and see if this fixes the situation.
I will try to test after overcoming bug #633358.
Both these versions are no longer in the tree. Please re-open if this is still an issue with current versions.