README.riscos: Improve the document
#12975
| Job | Run time |
|---|---|
| 10m 15s | |
| 10s | |
| 10m 15s | |
| 15m 30s | |
| 2h 0m 8s | |
| 9m 19s | |
| 14m 52s | |
| 11m 8s | |
| 34m 46s | |
| 50m 57s | |
| 17m 11s | |
| 9m 19s | |
| 9m 43s | |
| 9m 28s | |
| 21m 30s | |
| 2m 45s | |
| 9m 11s | |
| 23m 0s | |
| 2m 48s | |
| 9m 15s | |
| 22m 58s | |
| 2m 23s | |
| 2m 17s | |
| 9m 51s | |
| 5m 27s | |
| 9m 34s | |
| 3m 37s | |
| 8m 5s | |
| 23m 37s | |
| 7h 59m 19s |