[Build] Do not use unbounded DispatchIO readers for tar tranfers by wlan0 · Pull Request #257 · apple/container

@wlan0

- Addresses #166
- Memory utilization explodes since there is no mechanism for backpressure
- Using a synchronous buffered reader seem to provide similar performance without the memory explosion issue
- 4MB buffer seems to provide the best results

| Metric                   | 1MB Buffer | 4MB Buffer | Unbounded Zero-Copy |
|--------------------------|------------|------------|---------------------|
| Build Time               | 149.33s    | 138.57s    | 139.79s             |
| Max RAM Used             | 2.16 GB    | 3.02 GB    | 3.52 GB             |
| Peak Memory Footprint    | 8.30 GB    | 8.17 GB    | 10.21 GB            |
| Page Reclaims            | 1,085,559  | 1,039,677  | 1,619,943           |
| Page Faults              | 115        | 148        | 143                 |
| CPU Usage (User+Sys)     | 53.71s     | 53.12s     | 60.44s              |