Workaround rubygems $LOAD_PATH bug

[casperisfine]

Ref: #647
Ref: rubygems/rubygems#6490

Older rubygems are executing extconf.rb with a broken $LOAD_PATH causing the json gem native extension to be loaded with the stdlib version of the .rb files.

This fails with

json/common.rb:82:in `initialize': wrong number of arguments (given 1, expected 0) (ArgumentError)

Since this is just for extconf.rb we can probably just accept that extra argument and ignore it.

The bug was fixed in rubygems 3.4.9 / 2023-03-20

FYI: @pixeltrix

[casperisfine]

The problem is that this makes #646 somewhat worse, as it changes from a boot time issue into a runtime one.

$ bundle exec ruby -W -e 'require "json"; JSON.dump({})'
/Users/byroot/.gem/ruby/3.3.4/gems/json_pure-2.6.3/lib/json/common.rb:300: warning: The json gem extension was loaded with the stdlib ruby code. You should upgrade rubygems with `gem update --system`
/Users/byroot/.gem/ruby/3.3.4/gems/json_pure-2.6.3/lib/json/common.rb:310:in `generate': undefined method `configure' for an instance of JSON::Ext::Generator::State (NoMethodError)

      state = state.configure(opts)
                   ^^^^^^^^^^
	from /Users/byroot/.gem/ruby/3.3.4/gems/json_pure-2.6.3/lib/json/common.rb:641:in `dump'
	from -e:1:in `<main>'

The same code being shipped in json and json_pure is really a problem, I think we might need to namespace them somehow? Or find a way to enforce that both versions match.