disk-image-minimal: correctly type key

Author: brooksdavis

pycheribuild/projects/disk_image.py

@@ -342,7 +342,7 @@ def add_from_mtree(self, mtree_file, mtree_path, strip_binaries: "Optional[bool]
                 if not self.maybe_strip_elf_file(file, output_path=stripped_path):
                     stripped_path = contents
                 self.stripped_contents[contents] = stripped_path
-                self.stripped_contents[stripped_path] = stripped_path
+                self.stripped_contents[str(stripped_path)] = stripped_path
             else:
                 stripped_path = self.stripped_contents[contents]
             if stripped_path != contents: