Error while installing json gem 'mkmf.rb can't find header files for ruby'For context, it on a remote server which has a firewall. I'm setting up my environment through a proxy. I have ruby 1.8.7. When I try to gem install.. sudo gem install --http-proxy <host address>:<port> json I get the following error: Building native extensions. This could take a while... ERROR: Error installing json: ERROR: Failed to build gem native extension. /usr/bin/ruby extconf.rb mkmf.rb ca
