mkmf.rb: fix splitting options with an argument
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36918 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
mkmf.rb: fix splitting options with an argument
options with an argument, not using NUL as special character.
[ruby-core:47447] [Bug #6987]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@36918 b2dd03c8-39d4-4d8f-98ff-823fe69b080e