Pull in rules_rust

It needs some tweaks to actually work for our armv7 platform.

Signed-off-by: Brian Silverman <bsilver16384@gmail.com>
Change-Id: Icc7cb075e2409b7a060c1b30cde1366ce1e2d571
diff --git a/WORKSPACE b/WORKSPACE
index 31bc03c..8f2dd52 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -829,14 +829,9 @@
     urls = ["https://github.com/bazelbuild/rules_webtesting/releases/download/0.3.5/rules_webtesting.tar.gz"],
 )
 
-http_archive(
+local_repository(
     name = "rules_rust",
-    sha256 = "531bdd470728b61ce41cf7604dc4f9a115983e455d46ac1d0c1632f613ab9fc3",
-    strip_prefix = "rules_rust-d8238877c0e552639d3e057aadd6bfcf37592408",
-    urls = [
-        # `main` branch as of 2021-08-23
-        "https://github.com/bazelbuild/rules_rust/archive/d8238877c0e552639d3e057aadd6bfcf37592408.tar.gz",
-    ],
+    path = "third_party/rules_rust",
 )
 
 load("@rules_rust//rust:repositories.bzl", "rust_repository_set")