[llvm][bazel] Port 7f3afab

Author: chsigg

utils/bazel/llvm-project-overlay/llvm/BUILD.bazel

@@ -320,6 +320,7 @@ cc_library(
     deps = [
         ":config",
         ":Demangle",
+        "//third-party/siphash",
         # We unconditionally depend on the custom LLVM zlib wrapper. This will
         # be an empty library unless zlib is enabled, in which case it will
         # both provide the necessary dependencies and configuration defines.

utils/bazel/llvm-project-overlay/third-party/siphash/BUILD.bazel

@@ -0,0 +1,13 @@
+# This file is licensed under the Apache License v2.0 with LLVM Exceptions.
+# See https://llvm.org/LICENSE.txt for license information.
+# SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+package(default_visibility = ["//visibility:public"])
+
+licenses(["notice"])
+
+cc_library(
+	name = "siphash",
+	hdrs = ["include/siphash/SipHash.h"],
+	strip_include_prefix = "include",
+)