HPCC-31335 update build-assets.yml for Rocky Linux 8 support

[xwang2713]

This fix depends on HPCC-31585 "need rpm-build package in rockylinux-8.dockerfile"
This PR includes following changes:

HPCC-Platform/cmake_modules/distrocheck.sh
HPCC-Platform/.github/workflows/build-assets.yml (remove centos-8 and add rockylinux-8)
"centos-8" and "rockylinux-8" will generate the same rpm file name (el8) since both are based on RedHat Enterprise 8

Type of change:

• This change is a bug fix (non-breaking change which fixes an issue).
• This change is a new feature (non-breaking change which adds functionality).
• This change improves the code (refactor or other change that does not change the functionality)
• This change fixes warnings (the fix does not alter the functionality or the generated code)
• This change is a breaking change (fix or feature that will cause existing behavior to change).
• This change alters the query API (existing queries will have to be recompiled)

Checklist:

• My code follows the code style of this project.
  • My code does not create any new warnings from compiler, build system, or lint.
• The commit message is properly formatted and free of typos.
  • The commit message title makes sense in a changelog, by itself.
  • The commit is signed.
• My change requires a change to the documentation.
  • I have updated the documentation accordingly, or...
  • I have created a JIRA ticket to update the documentation.
  • Any new interfaces or exported functions are appropriately commented.
• I have read the CONTRIBUTORS document.
• The change has been fully tested:
  • I have added tests to cover my changes.
  • All new and existing tests passed.
  • I have checked that this change does not introduce memory leaks.
  • I have used Valgrind or similar tools to check for potential issues.
• I have given due consideration to all of the following potential concerns:
  • Scalability
  • Performance
  • Security
  • Thread-safety
  • Cloud-compatibility
  • Premature optimization
  • Existing deployed queries will not be broken
  • This change fixes the problem, not just the symptom
  • The target branch of this pull request is appropriate for such a change.
• There are no similar instances of the same problem that should be addressed
  • I have addressed them here
  • I have raised JIRA issues to address them separately
• This is a user interface / front-end modification
  • I have tested my changes in multiple modern browsers
  • The component(s) render as expected

Smoketest:

• Send notifications about my Pull Request position in Smoketest queue.
• Test my draft Pull Request.

Testing:

Test builds for CE/LN Platform, Plugins and Clienttools.
CE Platform: https://github.com/xwang2713/github-action-dev-build/actions/runs/8602704671/artifacts/1395342307
LN Platform: https://github.com/xwang2713/github-action-dev-build/actions/runs/8609938825/artifacts/1396435287
Plugins and Clienttools package included in this zip file: https://github.com/xwang2713/github-action-dev-build/actions/runs/8616127030/artifacts/1398169920

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-31335

Jirabot Action Result:
Additional PR: #18542

[GordonSmith]

@xwang2713 can you review my changes to your PR and squash if happy?

[GordonSmith]

@xwang2713 you also need to sign your commit and fill in the checkboxes - thx.

[GordonSmith]

See above.

[GordonSmith]

@xwang2713 bump

[xwang2713]

Done

[GordonSmith]

Closing and opening to trigger tests.

[github-actions]

Jira Issue: https://hpccsystems.atlassian.net//browse/HPCC-31335

Jirabot Action Result:
Additional PR: #18542