proper cleanup;

--- a/src/Pure/Admin/build_release.scala	Sun Jan 22 22:48:12 2023 +0100
+++ b/src/Pure/Admin/build_release.scala	Sun Jan 22 22:48:51 2023 +0100
@@ -796,6 +796,8 @@
               Bytes.read(sfx_exe) + Bytes(sfx_txt) + Bytes.read(exe_archive))
             File.set_executable(context.dist_dir + isabelle_exe, true)
         }
+
+        other_isabelle.cleanup()
       }
       progress.echo("DONE")
     }