src/Pure/Tools/build.scala

     verbose: Boolean, browser_info: Path)
   {
     // global browser info dir
     if (info.options.bool("browser_info") && !(browser_info + Path.explode("index.html")).is_file)
     {
-      browser_info.file.mkdirs()
+      Isabelle_System.mkdirs(browser_info)
       File.copy(Path.explode("~~/lib/logo/isabelle.gif"),
         browser_info + Path.explode("isabelle.gif"))
       File.write(browser_info + Path.explode("index.html"),
         File.read(Path.explode("~~/lib/html/library_index_header.template")) +
         File.read(Path.explode("~~/lib/html/library_index_content.template")) +

         (output_dir :: Isabelle_System.find_logics_dirs(), output_dir,
          Path.explode("$ISABELLE_BROWSER_INFO"))
       }
 
     // prepare log dir
-    (output_dir + LOG).file.mkdirs()
+    Isabelle_System.mkdirs(output_dir + LOG)
 
     // optional cleanup
     if (clean_build) {
       for (name <- full_tree.graph.all_succs(selected)) {
         val files =