ci(release): use --if-present flag when running build script

Author: gr2m

.github/workflows/release.yml

@@ -17,7 +17,7 @@ jobs:
         with:
           node-version: 12
       - run: npm ci
-      - run: npm run build
+      - run: npm run build --if-present
       - run: npx semantic-release
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}