fix(dev-infra): add missing BUILD file to dev-infra/bazel:files (#38026)

* Without this BUILD file we were seeing errors about the reference to
  expand_template.bzl in ng_rollup_bundle.bzl because dev-infra/bazel
  was not considered a package.

PR Close #38026

dev-infra/bazel/BUILD.bazel

@@ -3,6 +3,7 @@ package(default_visibility = ["//visibility:public"])
 filegroup(
     name = "files",
     srcs = [
+        "BUILD.bazel",
         "expand_template.bzl",
     ],
 )