CI: pin nightly version to 2022-11-01

[tarcieri]

A pinned nightly may potentially work around the build failures we're experiencing due to build scripts using SIMD features:

#433 (comment)

[tarcieri]

This seems to have recently popped up, so it seems that LLVM might be auto-vectorizing some code in the build script it previously didn't used to.

Hopefully pinning the nightly version provides a band-aid and also keeps the build reproducibly green. However it doesn't actually solve the problem of the build failing on missing AVX intrinsics.

[rozbb]

I can't seem to replicate the build error on my x86-64 machine. On release/4.0 I'm running cargo +nightly test --features "simd_backend" Should that produce an error?

[tarcieri]

It appears to be dying when these RUSTFLAGS are used:

RUSTFLAGS="-C target_feature=+avx512ifma"

I managed to reproduce it locally:

$ RUSTFLAGS="-C target_feature=+avx512ifma" cargo +nightly test --features "simd_backend"
   Compiling autocfg v1.1.0
   [...]
   Compiling ciborium-ll v0.2.0
error: failed to run custom build command for `proc-macro2 v1.0.47`

Caused by:
  process didn't exit successfully: `/Users/bascule/src/dalek-cryptography/curve25519-dalek/target/debug/build/proc-macro2-1ea3ba4a89c1184f/build-script-build` (signal: 4, SIGILL: illegal instruction)

[tarcieri]

Hmm, it seems while this nightly version "fixed" the issue in CI, it's still failing locally for me

[rozbb]

Same, even after a cargo clean

[rozbb]

Not for me 😕

[tarcieri]

Might've found a workaround: #436

[tarcieri]

I think #436 is working. Closing this.