[ROOT6] Updated root to tip of branch master: LLVM 20

[smuzaffar]

Testing latest root master branch changes which now uses LLVM 20

[smuzaffar]

test parameters:

• full_cmssw = true
• enable = threading

[cmsbuild]

A new Pull Request was created by @smuzaffar for branch IB/CMSSW_16_0_X/rootmaster.

@akritkbehera, @cmsbuild, @iarspider, @smuzaffar can you please review it and eventually sign? Thanks.
@ftenchini, @mandrenguyen, @sextonkennedy you are the release manager for this.
cms-bot commands are listed here

[cmsbuild]

cms-bot internal usage

[smuzaffar]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-faab7e/48570/summary.html
COMMIT: e9e027d
CMSSW: CMSSW_16_0_ROOT6_X_2025-10-08-2300/el8_amd64_gcc13
Additional Tests: THREADING
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmsdist/10118/48570/install.sh to create a dev area with all the needed externals and cmssw changes.

The following merge commits were also included on top of IB + this PR after doing git cms-merge-topic:

• @akritkbehera [FWCore] Fix segmentation fault in testRefInROOT::testGoodChain when using TChain cmssw#49103
• @pietroGru cmsDriver.py "command line options" readiness for copy-paste cmssw#48985

You can see more details here:
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-faab7e/48570/git-recent-commits.json
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-faab7e/48570/git-merge-result

Comparison Summary

Summary:

• You potentially added 109 lines to the logs
• Reco comparison results: 47 differences found in the comparisons
• DQMHistoTests: Total files compared: 51
• DQMHistoTests: Total histograms compared: 3940073
• DQMHistoTests: Total failures: 3519
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3936534
• DQMHistoTests: Total skipped: 20
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 50 files compared)
• Checked 218 log files, 188 edm output root files, 51 DQM output files
• TriggerResults: no differences found

[smuzaffar]

closing in favor of #10120