as per bug #113758 and ferringb in the g.portage-dev thread 'confcache, final chance to ixnay it', dev-lang/ruby needs to be restricted from using confcache. ruby's configure incorrectly caches the results of -lcrypt detection, along with other checks that haven't yet been identified. adding RESTRICT="confcache" to the ebuild will keep these and other yet undetected errors from polluting the cache.
fixed.