Ensure that Doc/dist exists (#271)

Author: AA-Turner

build_docs.py

@@ -817,6 +817,7 @@ def copy_build_to_webroot(self, http: urllib3.PoolManager) -> None:
         if not self.quick:
             # Copy archive files to /archives/
             logging.debug("Copying dist files.")
+            (self.checkout / "Doc" / "dist").mkdir(exist_ok=True)
             run([
                 "chown",
                 "-R",