山本です。

MAIN の make distclean が失敗します。ruby_1_8 のほうは大丈夫です。

E:\ruby-cvs\ruby>make distclean
MAKE Version 5.2  Copyright (c) 1987, 2000 Borland
cleaning Win32API
./ext/extmk.rb:98:in `+': cannot convert nil into String (TypeError)
        from ./ext/extmk.rb:98:in `extmake'
        from ./ext/extmk.rb:98:in `map'
        from ./ext/extmk.rb:98:in `extmake'
        from ./ext/extmk.rb:290
        from ./ext/extmk.rb:289:in `each'
        from ./ext/extmk.rb:289