Don't call rb_str_set_len while released the GVL.
#201
| Job | Run time |
|---|---|
| 4s | |
| 23s | |
| 2m 34s | |
| 28s | |
| 32s | |
| 2m 51s | |
| 22s | |
| 31s | |
| 4m 21s | |
| 13s | |
| 12s | |
| 1m 13s | |
| 11s | |
| 14s | |
| 1m 19s | |
| 10s | |
| 14s | |
| 1m 31s | |
| 10s | |
| 15s | |
| 2m 55s | |
| 10s | |
| 20s | |
| 30s | |
| 21s | |
| 1m 34s | |
| 1m 0s | |
| 24m 38s |