CI: Save iverilog cache in action

We still want to cache iverilog even if the rest of the action fails, so explicitly save/restore instead of standard cache.

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

@@ -45,7 +45,7 @@ runs:
         echo "procs=$(sysctl -n hw.ncpu)" >> $GITHUB_ENV
 
     - name: Setup iverilog
-      if: inputs.get-iverilog
+      if: inputs.get-iverilog == 'true'
       uses: ./.github/actions/setup-iverilog
       with:
         runs-on: ${{ inputs.runs-on }}