Fix: Usage with PNPM on Windows

[bestickley]

Problem

When using cdk-nextjs with PNPM on windows, the deployment succeeds but server fails with 500 because it cannot find "next" package. This is because PNPM uses symlinks and the during deployment, cdk-nextjs uses Compress-Archive powershell commandlet which doesn't support symlinks.

Solution

Use fs.cpSync with dereference: true to get rid of symlinks and copy to a temporary location. Then use built in CDK Asset construct to upload.