Update build of rubygem interception

[bkmgit]

When compiling from source, the build of interception, one gets the message

Compiling native extension in /home/user/SonicPi/sonic-pi/app/server/ruby/vendor/interception/ext
make: *** No rule to make target 'clean'.  Stop.

As indicated in its extconf.rb file, compilation is only needed if using JRuby or MRI < 2.0. As MRI < 2.0 are out of support, one should check for JRuby (if supported) and otherwise not compile.

The generated Makefile does not have a clean command, so that should not be run in: https://github.com/sonic-pi-net/sonic-pi/blob/dev/app/server/ruby/bin/compile-extensions.rb#L70

[bkmgit]

Could also be removed from the setup part as done in https://github.com/audinux/fedora-spec/blob/master/sonic-pi/sonic-pi.spec

[samaaron]

@bkmgit - thanks for the heads up. I actually just removed a bunch of cruft from the Ruby vendor dir which includes interception. So hopefully this issue is now resolved.