RBE: Update toolchain with bazel-toolchains 5.1.2 release

Due to this platform style migration: [1] the RBE toolchain needs to be
updated to use the latest rbe_config_gen from bazel-toolchains (at least
version 5.1.2 so that it contains: [2]).

This change makes RBE build forwards compatible so that Bazel could be
updated to the upcoming major 6.0 release.

[1] https://github.com/bazelbuild/bazel/issues/8622
[2] https://github.com/bazelbuild/bazel-toolchains/commit/8c717f8258cd5f6c7a45b97d974292755852b658

Release-Notes: skip
Forward-Compatible: checked
Change-Id: Ib7f97db25e498252d746f8f49476676890849271
diff --git a/WORKSPACE b/WORKSPACE
index e5c5d4a..cf399dc 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -42,11 +42,11 @@
 
 http_archive(
     name = "rbe_jdk11",
-    sha256 = "5939e2a4e56d1fc53b6c44c6db97ee068c9f4bd18e86c762f6ab8b4fff5e294b",
-    strip_prefix = "rbe_autoconfig-3.0.0",
+    sha256 = "dbcfd6f26589ef506b91fe03a12dc559ca9c84699e4cf6381150522287f0e6f6",
+    strip_prefix = "rbe_autoconfig-3.1.0",
     urls = [
-        "https://gerrit-bazel.storage.googleapis.com/rbe_autoconfig/v3.0.0.tar.gz",
-        "https://github.com/davido/rbe_autoconfig/archive/v3.0.0.tar.gz",
+        "https://gerrit-bazel.storage.googleapis.com/rbe_autoconfig/v3.1.0.tar.gz",
+        "https://github.com/davido/rbe_autoconfig/archive/v3.1.0.tar.gz",
     ],
 )