proper Path conversion for Windows (amending b7554954d697);

--- a/src/Pure/System/isabelle_platform.scala	Mon Sep 08 19:37:25 2025 +0200
+++ b/src/Pure/System/isabelle_platform.scala	Mon Sep 08 20:52:55 2025 +0200
@@ -57,7 +57,7 @@
     def progress: Progress
 
     def standard_path(path: Path): String =
-      mingw.standard_path(File.standard_path(path))
+      mingw.standard_path(File.platform_path(path))
 
     def execute(cwd: Path, script_lines: String*): Process_Result = {
       val script = cat_lines("set -e" :: script_lines.toList)