Compile with the JIT

[coderanger]

For 3.13 and above the experimental JIT could be activated in the build but disabled by default. Adding --enable-experimental-jit=yes-off carries minimal risk and allows end-users to activate JIT support with the $PYTHON_JIT environment variable. Mostly creating this for tracking purposes.

This looks to be relatively low risk but would require installing LLVM during the compile. Shouldn't increase the resulting image size as it can be removed before the end of the build step.

[tianon]

The fact that upstream still considers it experimental gives me extreme pause -- I'd really hate for that "minimal" to become accidentally load-bearing. 😬

(#947 (comment) is somewhere else this has been mentioned, FWIW)

[coderanger]

With these images frequently being used for local development and the like, I think it being supported here will be an important step in getting it from "experimental" to "trusted" :) Wouldn't advocate it being turned on for production web servers but the image is used for a lot more than that.