Created attachment 515358 [details]
`emerge -1 '=dev-lang/ruby-2.2.9`ing results in a build failure with the message `[FATAL] Failed to create timer thread: Invalid argument`. Build logs are attached.
Created attachment 515360 [details]
emerge --info '=dev-lang/ruby-2.2.9::gentoo'
I can't reproduce this and it doesn't look familiar.
Can you test with ruby 2.3.6 as well? That version is in the process of being marked stable and 2.2.9 will be removed soonish.
ruby 2.3.9 as well as 2.5.0 build fine.