Add a semaphore to smg_uart_write so debug output doesn't get garbled
#2233
| Job | Run time |
|---|---|
| 1s | |
| 1s | |
| 17m 48s | |
| 1s | |
| 20m 36s | |
| 20m 36s | |
| 20m 35s | |
| 18m 44s | |
| 5m 57s | |
| 5m 21s | |
| 5m 17s | |
| 1h 54m 57s |