ext_conf_builder.rb: use RUBYOPT
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39559 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
ext_conf_builder.rb: use RUBYOPT
use RUBYOPT instead of -r option, and revert some tests. [Bug #7698]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@39559 b2dd03c8-39d4-4d8f-98ff-823fe69b080e