npm script to both build typescript files and run after deploying to AWS EB environment

I want AWS EB to automatically build and run my files without me having to explicitly build everytime I push to git repo. I've tried placing this in "scripts" in package.json:

"start": "tsc build && node build/index.js"

The outDir specified in my tsconfig.json is build. This unfortunately didn't work and I get 'Degraded' health status. I know this is definitely the problem with my web server, because I tried manually building and placing node build/index.js in the "start" script, and it worked. Here's my package.json:

{
  "name": "woocommerce-api",
  "version": "1.0.0",
  "description": "",
  "main": "src/index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1",
    "start": "npx tsc && node build/index.js",
    "dev": "nodemon -r dotenv/config src/index.ts",
    "deploy": "npm run build && node build/index.js",
    "build": "npx tsc"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "dependencies": {
    "@types/node": "^18.7.18",
    "cors": "^2.8.5",
    "dotenv": "^16.0.2",
    "express": "^4.18.1",
    "helmet": "^6.0.0",
    "nodemon": "^2.0.20"
  },
  "devDependencies": {
    "@types/cors": "^2.8.12",
    "@types/express": "^4.17.14",
    "@types/helmet": "^4.0.0",
    "@typescript-eslint/eslint-plugin": "^5.38.0",
    "@typescript-eslint/parser": "^5.38.0",
    "eslint": "^8.23.1",
    "ts-node": "^10.9.1",
    "typescript": "^4.8.3"
  }
}

And my simple app with a get path at home, and a post path at /hook to consume webhooks.

import express, { Response, Request } from "express";
import cors from "cors";
import helmet from "helmet";

const app = express();
app.use(cors());
app.use(helmet());
app.use(express.json());

const port = process.env.PORT || 8081;

app.get("/", (req: Request, res: Response) => {
  res.send({ message: "Hello world1234" });
});

app.post("/hook", (req: Request, res: Response) => {
   console.log(req.body);
   res.status(200).send({ message: "success" });
});

app.listen(port, () => {
  console.log(`Listening on port ${port}...`);
});

Would appreciate the help.