Update spack submodule from spack develop

[AlexanderHrabski-NOAA]

Description

Updates the spack submodule to use the latest commits from spack/spack:develop as of 2026/05/20, including the new parallel installer.

Dependencies

• Requires Update spack-stack-dev from spack develop 2026/05/20 spack#577

Issues addressed

None.

Applications affected

All applications are affected.

Systems affected

All systems are affected.

Testing

• CI: Note whether the automatic tests (GitHub actions tests that run automatically for every commit) pass or not
  • GitHub actions CI tests pass
  • GitHub actions CI tests do not pass (provide explanation)
  • GitHub actions CI tests skipped (provide explanation if necessary)
• New tests added: List and describe any new tests added to GitHub actions
  • ...
• Additional testing: Add information on any additional tests conducted
  • ...

Checklist

• This PR addresses one issue/problem/enhancement or has a very good reason for not doing so.
• These changes have been tested on the affected systems and applications.
• All dependency PRs/issues have been resolved and this PR can be merged.
• All necessary updates to the documentation (spack-stack wiki) will be made when this PR is merged

[climbfuji]

What's the default installer if none is specified (we don't)? The old or the new one?

[AlexanderHrabski-NOAA]

I'm not seeing explicit reference in the docs to selecting the old installer, but the default behavior as far as the TUI goes is context dependent. It appears if the process is not tty, it will run in a non-interactive mode.
https://spack.readthedocs.io/en/latest/installing.html#non-interactive-mode

That said, the old parallel build behavior amounted to something like spack install -j16 -p1 with the new installer for a 16 thread build. The new feature is package-level concurrency.

[AlexanderHrabski-NOAA]

Looking through the release notes from 2025-11-14, the old installer can be selected via:
spack config add config:installer:old
https://github.com/spack/spack/releases
I confirmed this on my system. The default behavior is to use the new installer. Also, I found a todo list that suggest the new installer is very close to feature parity with the old installer:
spack/spack#51515

[climbfuji]

I notice the CI tests were all failing. Maybe you can take a look at what's going on?

I also suggest waiting with pushing any bug fixes or updates from develop until #2026 is merged.