current directory:/usr/lib64/ruby/gems/2.1.0/gems/ffi-1.9.18/ext/ffi_c/usr/bin/ruby.ruby2.1-r ./siteconf20170501-19647-33n3uw.rb extconf.rb mkmf.rb can't find header files for ruby at /usr/lib64/ruby/include/ruby.hextconf failed, exit code1Gem files will remain installedin/usr/l...