mingw: Fix CFLAGS for winpthreads.
#18238
| Job | Run time |
|---|---|
| 2h 53m 17s | |
| 2h 53m 17s | |
| 4h 54m 56s | |
| 4h 54m 56s | |
| 1h 54m 36s | |
| 1h 54m 36s | |
| 2h 55m 27s | |
| 2h 55m 27s | |
| 1h 31m 28s | |
| 1h 31m 28s | |
| 1h 19m 49s | |
| 1h 19m 49s | |
| 4h 31m 44s | |
| 4h 31m 44s | |
| 1h 39m 33s | |
| 1h 39m 33s | |
| 27m 59s | |
| 27m 59s | |
| 27m 57s | |
| 1h 9m 11s | |
| 1d 21h 54m 46s |