fix(ci): install aarch64 cross compiler for Miri job

criterion 0.8.2 pulls in the `alloca` dev-dependency, whose build script
cross-compiles C. The aarch64 Miri step (`cargo miri test --target
aarch64-unknown-linux-gnu`) failed because the runner has no
`aarch64-linux-gnu-gcc`. Install gcc-aarch64-linux-gnu so cc-rs can find
it.

Author: heeckhau

.github/workflows/rust.yml

@@ -109,6 +109,14 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      # The `alloca` crate (a dev-dependency pulled in via criterion) has a
+      # build script that cross-compiles C, which needs an aarch64 C compiler
+      # for the aarch64 Miri target.
+      - name: Install aarch64 cross compiler
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y gcc-aarch64-linux-gnu
+
       - name: Install Miri
         run: |
           rustup toolchain install nightly --component miri