CI: iverilog setup as composite action

Called during setup-build-env.

.github/actions/setup-build-env/action.yml

@@ -5,6 +5,11 @@ inputs:
   runs-on:
     required: true
     type: string
+  get-iverilog:
+    description: 'Install iverilog'
+    default: false
+    required: false
+    type: boolean
 
 runs:
   using: composite
@@ -38,3 +43,9 @@ runs:
         echo "$(brew --prefix bison)/bin" >> $GITHUB_PATH
         echo "$(brew --prefix flex)/bin" >> $GITHUB_PATH
         echo "procs=$(sysctl -n hw.ncpu)" >> $GITHUB_ENV
+
+    - name: Setup iverilog
+      if: inputs.get-iverilog
+      uses: ./.github/actions/setup-iverilog
+      with:
+        runs-on: ${{ inputs.runs-on }}