ci: Add job to check the MSRV build of uefi-raw

The `uefi-raw` package has a lower MSRV than the `uefi` package, so it needs to
be tested separately.

Author: nicholasbishop

.github/workflows/rust.yml

@@ -134,6 +134,25 @@ jobs:
         run: |
           cargo --version
           cargo build --target x86_64-unknown-uefi -p uefi-test-runner
+  # The uefi-raw crate has its own MSRV. Check that the crate builds correctly
+  # with that version of the toolchain.
+  build_msrv_raw:
+    name: Build (uefi-raw MSRV)
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+      - name: Set toolchain
+        run: |
+          # Extract the MSRV using cargo.
+          msrv=$(cargo metadata --no-deps --format-version=1 | jq --raw-output '.packages[] | select(.name == "uefi-raw") | .rust_version')
+          echo "MSRV: ${msrv}"
+          # Set the MSRV in the toolchain config.
+          sed -i "s:stable:${msrv}:" rust-toolchain.toml
+      - name: Build
+        run: |
+          cargo --version
+          cargo build -p uefi-raw
   # This job requires the nightly channel, but keep it as a separate job from
   # `nightly_channel` because it takes a while to run.
   build_feature_permutations: