win32/Makefile.sub: copy enc/jis/props.h

* win32/Makefile.sub (enc/jis/props.h): nmake needs special rule
  to copy from the source directory, because it can't handle VPATH.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@46128 b2dd03c8-39d4-4d8f-98ff-823fe69b080e