mach: CI: fix Apple Silicon builder

Signed-off-by: Stephen Gutekanst <stephen@hexops.com>

.github/workflows/m1_ci.yml

@@ -26,6 +26,8 @@ jobs:
           rm -rf $GITHUB_WORKSPACE && mkdir $GITHUB_WORKSPACE
       - name: Checkout
         uses: actions/checkout@v2
+        with:
+          submodules: 'true'
       - name: test
         run: zig build test
       - name: build