Update setup.sh: add export SPACK_DISABLE_LOCAL_CONFIG=true

[climbfuji]

Summary

Update setup.sh: add export SPACK_DISABLE_LOCAL_CONFIG=true to completely isolate the spack-stack environments from user spack configurations. This requires additional steps to unset and restore the environment variable when creating new site configurations. Further, remove the exception for macOS (no longer needed, see #1545 (comment) below for more information)

Testing

• Tested on NRL systems and @climbfuji's devbox
• CI

Applications affected

None

Systems affected

"All" (not really), but at least air-gapped systems where the spack bootstrap mirror needs to be used every time from now on.

Dependencies

n/a

Issue(s) addressed

Closes #1544

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.

[RatkoVasic-NOAA]

LGTM

[climbfuji]

Ooops, I remember. The problem was this didn't work for new site configs, because we use spack external find --scope=system. I will look into other options (scope=site, for example).

[climbfuji]

I fixed this in 2e91ad6, a17b244, and d42cf47 by adding one more step to the NewSiteConfig instructions (unset SPACK_DISABLE_LOCAL_CONFIG when setting SPACK_SYSTEM_CONFIG_PATH, and restoring SPACK_DISABLE_LOCAL_CONFIG when unsetting SPACK_SYSTEM_CONFIG_PATH). Same for GitHub actions CI runs.

I also removed the exception to skip avoiding ~/.spack for macOS. We needed this in the past when bootstrapping was a tedious and manual process, but fortunately this is no longer the case. I tested this on the macOS CI runner manally. Hopefully, it will work just as well in CI.

[srherbener]

I think this looks good. I did not test, rather I'm relying on the CI testing and others. I like that by default user configuration is ignored for the build, and only for customized (new site config) builds you can temporarily enable user configuration. Thanks!