Update bazel_toolchains to latest release and add toolchain config target for BuildKite CI (rbe_ubuntu1604)

RELNOTES: None.
PiperOrigin-RevId: 237233612

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index b6346ea..8b5f465 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -229,14 +229,20 @@
 
 http_archive(
     name = "bazel_toolchains",
-    sha256 = "109a99384f9d08f9e75136d218ebaebc68cc810c56897aea2224c57932052d30",
-    strip_prefix = "bazel-toolchains-94d31935a2c94fe7e7c7379a0f3393e181928ff7",
+    sha256 = "4b1468b254a572dbe134cc1fd7c6eab1618a72acd339749ea343bd8f55c3b7eb",
+    strip_prefix = "bazel-toolchains-d665ccfa3e9c90fa789671bf4ef5f7c19c5715c4",
     urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/94d31935a2c94fe7e7c7379a0f3393e181928ff7.tar.gz",
-        "https://github.com/bazelbuild/bazel-toolchains/archive/94d31935a2c94fe7e7c7379a0f3393e181928ff7.tar.gz",
+      "https://mirror.bazel.build/github.com/bazelbuild/bazel-toolchains/archive/d665ccfa3e9c90fa789671bf4ef5f7c19c5715c4.tar.gz",
+      "https://github.com/bazelbuild/bazel-toolchains/archive/d665ccfa3e9c90fa789671bf4ef5f7c19c5715c4.tar.gz",
     ],
 )
 
+# Creates toolchain configuration for remote execution with BuildKite CI
+# for rbe_ubuntu1604.
+# To run the tests with RBE on BuildKite CI uncomment the two lines below
+# load("@bazel_toolchains//rules:rbe_repo.bzl", "rbe_autoconfig")
+# rbe_autoconfig(name = "buildkite_config")
+
 # We're pinning to a commit because this project does not have a recent release.
 # Nothing special about this commit, though.
 http_archive(