[ruby] fixing path to gcc such that users can use gem to install nati… (#17141)

* [ruby] fixing path to gcc such that users can use gem to install native gems to their home directory

* [ruby] working on making flake8 happier

* [ruby] Line can't really be split cleanly. Enhancing flake8's calm.

ya learn something new every day...

* [ruby] line break where requested

* [ruby] make raw string

* [ruby] only running for x86_64-linux everything else is untested

* [ruby] finding rbconfig.rb in a cross platform manner