[Bazel] Add `@llvm_zstd` to WORKSPACE (#2049)

This un-breaks Bazel CI since b31c5fa1fb.

Manually triggered GHA: 
- https://github.com/sjain-stanford/torch-mlir/actions/runs/4764744603 (failed)
- https://github.com/sjain-stanford/torch-mlir/actions/runs/4769130681 (with buildifier fix)

utils/bazel/WORKSPACE.bazel

@@ -3,6 +3,7 @@
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
+load("@bazel_tools//tools/build_defs/repo:utils.bzl", "maybe")
 
 http_archive(
     name = "bazel_skylib",
@@ -113,3 +114,14 @@ http_archive(
         "https://github.com/bazelbuild/buildtools/archive/refs/tags/4.2.2.tar.gz",
     ],
 )
+
+maybe(
+    http_archive,
+    name = "llvm_zstd",
+    build_file = "@llvm-raw//utils/bazel/third_party_build:zstd.BUILD",
+    sha256 = "7c42d56fac126929a6a85dbc73ff1db2411d04f104fae9bdea51305663a83fd0",
+    strip_prefix = "zstd-1.5.2",
+    urls = [
+        "https://github.com/facebook/zstd/releases/download/v1.5.2/zstd-1.5.2.tar.gz",
+    ],
+)