Merge pull request #4905 from kishima/cygwin_compile

Add double quotes for cygwin filenames #4904

lib/mruby/build.rb

@@ -280,7 +280,7 @@ EOS
       if name.is_a?(Array)
         name.flatten.map { |n| cygwin_filename(n) }
       else
-        `cygpath -w "#{filename(name)}"`.strip
+        '"%s"' % `cygpath -w "#{filename(name)}"`.strip
       end
     end