Add CI job for -Zdirect-minimal-versions.

Author: kpreid

.github/workflows/ci.yml

@@ -334,6 +334,69 @@ jobs:
                 --package naga \
                 --all-features --no-deps --document-private-items
 
+  # Check that the libraries build — but not that there are no warnings or that tests pass -
+  # with `-Zdirect-minimal-versions` which lowers all dependencies from the workspace packages
+  # to non-workspace packages to their minimum allowed version.
+  check-minimal-versions:
+    timeout-minutes: 10
+    
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          # Windows
+          - name: Windows x86_64
+            os: windows-2022
+            target: x86_64-pc-windows-msvc
+
+          # MacOS
+          - name: MacOS x86_64
+            os: macos-14
+            target: x86_64-apple-darwin
+
+          # Linux
+          - name: Linux x86_64
+            os: ubuntu-22.04
+            target: x86_64-unknown-linux-gnu
+
+    name: Minimal dependency versions check ${{ matrix.name }}
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v4
+
+      - name: Install toolchain (repo MSRV - tier 1 or 2)
+        if: matrix.tier == 1 || matrix.tier == 2
+        run: |
+          rustup toolchain install nightly --no-self-update --profile=minimal
+          rustup override set nightly
+          cargo -V
+
+      - name: Disable debug symbols
+        shell: bash
+        run: |
+          mkdir -p .cargo
+
+          cat <<EOF >> .cargo/config.toml
+            [profile.dev]
+            debug = false
+          EOF
+
+      - name: Caching
+        uses: Swatinem/rust-cache@v2
+        with:
+          key: clippy-${{ matrix.target }}-${{ matrix.kind }}-${{ env.CACHE_SUFFIX }}
+
+      - run: cargo update -Zdirect-minimal-versions
+
+      - name: Check
+        shell: bash
+        run: |
+          set -e
+
+          cargo check --target ${{ matrix.target }} ${{ matrix.extra-flags }} --all-targets --all-features
+
   # We run minimal checks on the MSRV of the core crates, ensuring that
   # its dependency tree does not cause issues for firefox.
   #