cmake: avoid -Wnonnull warning in HAVE_FSETXATTR_5 detection
#4210
| Job | Run time |
|---|---|
| 4m 30s | |
| 2m 21s | |
| 4m 39s | |
| 16m 26s | |
| 2m 26s | |
| 2m 32s | |
| 13m 14s | |
| 16m 49s | |
| 2m 17s | |
| 1m 44s | |
| 1m 44s | |
| 41s | |
| 2m 29s | |
| 1m 49s | |
| 2m 47s | |
| 2m 1s | |
| 4m 55s | |
| 18m 11s | |
| 4m 31s | |
| 14m 22s | |
| 3m 24s | |
| 47s | |
| 2m 39s | |
| 2m 19s | |
| 6m 56s | |
| 4m 57s | |
| 2m 52s | |
| 2m 1s | |
| 5m 47s | |
| 11m 43s | |
| 5m 57s | |
| 5m 47s | |
| 2m 46s | |
| 2m 25s | |
| 2m 21s | |
| 15m 29s | |
| 1m 58s | |
| 4m 57s | |
| 3m 30s | |
| 2m 25s | |
| 2m 51s | |
| 3h 34m 19s |