Improve back2source for Ruby for corner cases

> There a few rarer oddities that may need separate tracking in a future issues:
> - gem with "native" code delivered as C/C++ ... here the compilation may happen at install time? we may need to do some ELF or related analysis. See https://rubygems.org/gems/sha3 or https://rubygems.org/gems/java_bin
> - gem with platform=java that are designed to work on JRuby only with a `--java.gem` name as in https://rubygems.org/gems/java_override or a jubdy suffix as in https://rubygems.org/gems/java_gem at https://rubygems.org/downloads/java_gem-0.1.0-jruby.gem
> - gen with bundled JARs https://rubygems.org/gems/bouncy-castle-java

_Originally posted by @pombredanne in [#1436](https://github.com/aboutcode-org/scancode.io/issues/1436#issuecomment-3018881766)_