check cpu architecture and OS for gnparser binary (close #31)

[dimus]

No description provided.

[LocoDelAssembly]

Perhaps it is best to match by platform? Windows build failed. Here are possible platforms based on nokogiri: https://rubygems.org/gems/nokogiri/versions

Also would make a step closer to #31

To get the platform I think there is a global constant RUBY_PLATFORM for that. At least seems available in irb.

GitHub doesn't seem to have arm runners yet so we won't be able to verify with CI unless we can run QEMU or something as part of the test.

[dimus]

hm I get:

irb(main):002> ENV['PLATFORM']
=> nil

Let me try with RUBY_PLATFORM (looks like for JRuby RUBY_PLATFORM is always 'Java'

Also checking for platform creates a lot of possible combinations, because platform names are not standardized :-/
(eg aarch64-linux on mac, arm-linux-gnueabihf on Pi are both arm linux)