Revert "extension: Remove docker buildx"

This reverts commit fff2d72.

extension.bzl

@@ -4,7 +4,7 @@ from a OpenROAD-flow-scripts docker image and provides rules for its
 build stages.
 """
 
-load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive", "http_file")
 load("@bazel_tools//tools/build_defs/repo:utils.bzl", "maybe")
 load("//:docker.bzl", "docker_pkg")
 
@@ -20,6 +20,14 @@ _default_tag = tag_class(
 )
 
 def _orfs_dependencies():
+    maybe(
+        http_file,
+        name = "com_github_docker_buildx_file",
+        executable = True,
+        sha256 = "8d486f0088b7407a90ad675525ba4a17d0a537741b9b33fe3391a88cafa2dd0b",
+        urls = ["https://github.com/docker/buildx/releases/download/v0.15.1/buildx-v0.15.1.linux-amd64"],
+    )
+
     maybe(
         http_archive,
         name = "com_github_nixos_patchelf_download",