This release brings another fix for pathologically slow cases of lock
creation as well as a new `--sh-boot` feature for creating PEXes that
boot via `/bin/sh` for more resilience across systems with differing
Python installations as well as offering lower boot latency.
* Support booting via `/bin/sh` with `--sh-boot`. (1721)
* Fix more pathologic lock creation slowness. (1723)