Add Scala 3 compilation to CI

.github/workflows/test.yml

@@ -134,6 +134,44 @@ jobs:
       - name: Compile with Mill
         run: ./mill __.compile
 
+  mill3:
+    name: compile scala-3 project with mill
+    runs-on: ubuntu-22.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: ${{ inputs.ref }}
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          distribution: 'adopt'
+          java-version: '21'
+      - name: Install CIRCT
+        id: install-circt
+        if: ${{ inputs.circt }}
+        uses: circt/[email protected]
+        with:
+          version: ${{ inputs.circt }}
+          github-token: ${{ github.token }}
+      # TODO have install-circt do this
+      - name: Set CHISEL_FIRTOOL_PATH and CIRCT_INSTALL_PATH
+        if: steps.install-circt.outcome == 'success'
+        run: |
+          bindir=$(dirname $(which firtool))
+          installdir=$(dirname $bindir)
+          echo "CHISEL_FIRTOOL_PATH=$bindir" >> "$GITHUB_ENV"
+          echo "CIRCT_INSTALL_PATH=$installdir" >> "$GITHUB_ENV"
+      - name: Print firtool version
+        if: steps.install-circt.outcome == 'success'
+        run: |
+          echo "The CIRCT version used is:" >> $GITHUB_STEP_SUMMARY
+          echo \`\`\` >> $GITHUB_STEP_SUMMARY
+          $CHISEL_FIRTOOL_PATH/firtool -version >> $GITHUB_STEP_SUMMARY
+          echo \`\`\` >> $GITHUB_STEP_SUMMARY
+      - name: Compile with Mill
+        run: ./mill chisel[3.3.3].compile
+
   doc:
     name: Formatting
     runs-on: ubuntu-22.04