build: replace bash-isms with sh-friendly test and case, cleanup
#180
| Job | Run time |
|---|---|
| 9s | |
| 5m 1s | |
| 6m 2s | |
| 4m 32s | |
| 4m 8s | |
| 5m 45s | |
| 5m 42s | |
| 5m 21s | |
| 5m 29s | |
| 4m 50s | |
| 46m 59s |