Only add "l" in MAKEFLAGS if not already there on Windows
Only add "l" in MAKEFLAGS if not already there on Windows

ruby/spec,eregon/rubyspec,ruby/spec,sgarciac/spec,ruby/rubyspec,nobu/rubyspec,ruby/spec,nobu/rubyspec,eregon/rubyspec,sgarciac/spec,nobu/rubyspec,eregon/rubyspec,sgarciac/spec,ruby/rubyspec