fix fetching of submodules which was broken by rust-lang/rust#97513

Author: matthiaskrgr

.github/workflows/rust.yml

@@ -38,7 +38,7 @@ jobs:
       - name: copy config.toml into rustc repo
         run: cp -f config.toml rust/config.toml
       - name: check out submodules
-        run: ./x.py
+        run: git submodule update --init
         working-directory: rust
       - name: clone icemaker
         run: git clone https://github.com/matthiaskrgr/icemaker icemaker