Update build script to install corepack and enable pnpm (#645)

Author: mdroidian

apps/roam/build.sh

@@ -1,5 +1,7 @@
 #!/bin/bash
 set -e
+npm install -g corepack@latest
+corepack enable pnpm
 pnpm install
 npx turbo run build --filter=roam
 cp dist/* .