docker-ruby-alpine-libv8 
This image is based on the official Ruby image for Alpine Linux. It contains
the libv8 gem installed with a V8 engine that's built against the
musl C library that Alpine Linux uses.
One can, of course, just install NodeJS in Alpine Linux and ExecJS will just use that. If you'd prefer not to use NodeJS, then you can use this image to base your app on.
Example
Here's what happens with the normal Alpine based Ruby image:
docker run -it --rm ruby:alpine sh
apk add build-base
gem install therubyracer
irb(main):001:0> require 'v8'
LoadError: Error relocating /usr/local/bundle/gems/therubyracer-0.12.3/lib/v8/init.so: __vfprintf_chk: symbol not found - /usr/local/bundle/gems/therubyracer-0.12.3/lib/v8/init.so
And here's it working with this image:
docker run -it --rm joenyland/ruby-alpine-libv8
apk add build-base
gem install therubyracer
irb(main):001:0> require 'v8'
=> true
irb(main):002:0> V8::Context.new.eval 5 * 9
=> 45