Add self-update feature for executable PIEs

[asgrim]

Discussed in #460

^{Originally posted by asgrim December 17, 2025}
#443 - slated for 1.4.0 release - introduces an experimental executable version of PIE. However, an initial limitation of this experimental functionality is that the self-update mechanism has been disabled.

If there is enough demand for the executable versions, we can fix this functionality.