Add a bzl_library target for toolchain_utils.bzl

Now that `toolchain_utils.bzl` loads other bzl files, this will be helpful for downstream tests that rely on this file.

PiperOrigin-RevId: 633436595
Change-Id: Ia9cbd6c200e5d526e7c860d268506b0b05fc6207

Author: hvadehra

toolchains/BUILD

@@ -1,3 +1,4 @@
+load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
 load("@rules_cc//cc:defs.bzl", "cc_library")
 load(
     ":default_java_toolchain.bzl",
@@ -321,3 +322,10 @@ java_runtime_version_alias(
     runtime_version = "8",
     visibility = ["//visibility:public"],
 )
+
+bzl_library(
+    name = "toolchain_utils",
+    srcs = ["toolchain_utils.bzl"],
+    visibility = ["//visibility:public"],
+    deps = ["//java/common"],
+)