This is just an issue to discuss upgrading to Z3 4.13.3.

Is this a good idea? I'm not sure.

Pros:

• no more emulation for Apple Silicon (4.8.5 does not work on aarch64)
• consistency with F* -- HACL* is not left behind using an older version of Z3
• elimination of long-standing z3 bugs ("vector overflow, internal error", etc.)

Cons:

• more work to update proofs, fix things up
• possible performance regressions
• users would have to fix their setups to have the proper symlinks.

Status is as follows:

• I have had a build running for a while, so far, no file has failed outright -- some had to have their rlimits bumped (via z3rlimit_factor, on the command-line), but no dealbreaker at this stage
• however, the build is not finished because some vale files are taking an outrageous amount of time:

[VERIFY] Vale.Curve25519.X64.FastSqr.fst, 49:22.94

What would be needed?

• Update nix flake, CI, build, etc.
• Proper checks in the build to make sure users have a proper setup
• Strengthen proofs and debug why Vale is taking so very long

CC @gebner @mtzguido @R1kM