Fix Build::compile_objects perf regression and deadlock
#758
| Job | Run time |
|---|---|
| 19s | |
| 39s | |
| 1m 28s | |
| 1m 45s | |
| 34s | |
| 36s | |
| 34s | |
| 1m 48s | |
| 1m 29s | |
| 1m 13s | |
| 1m 34s | |
| 1m 30s | |
| 1m 58s | |
| 1m 44s | |
| 2m 4s | |
| 2m 2s | |
| 21m 17s |