win32/setup.mak: remove each files

* win32/setup.mak (-runtime-): removing by wildcard errs on network
  file system, so remove each files.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@38773 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

win32/setup.mak

@@ -152,7 +152,7 @@ int main(int argc, char **argv)
 }
 <<
 	@.\rtname >>$(MAKEFILE)
-	@del rtname.*
+	@for %I in (rtname.*) do @del %I
 
 -version-: nul
 	@$(APPEND)