Create skeleton for a Rust backend.

This code is experimental and should not be expected to emit working code, and callers are liable to break without warning.

It is being released now so that development can occur in the open, but users should not expect this to be supported any time soon.

PiperOrigin-RevId: 508095929

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index e68cd88..2301093 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -127,3 +127,13 @@
     name = "python_headers",
     actual = "@system_python//:python_headers",
 )
+
+http_archive(
+    name = "rules_rust",
+    sha256 = "d125fb75432dc3b20e9b5a19347b45ec607fabe75f98c6c4ba9badaab9c193ce",
+    urls = ["https://github.com/bazelbuild/rules_rust/releases/download/0.17.0/rules_rust-v0.17.0.tar.gz"],
+)
+
+load("@rules_rust//rust:repositories.bzl", "rules_rust_dependencies", "rust_register_toolchains")
+rules_rust_dependencies()
+rust_register_toolchains()