[ROOT] Allow submodules to contain headers missing headers

[smuzaffar]

Fixes cms-sw/cmssw#39735

[smuzaffar]

please test

[cmsbuild]

A new Pull Request was created by @smuzaffar (Malik Shahzad Muzaffar) for branch IB/CMSSW_12_6_X/master.

@smuzaffar, @aandvalenzuela, @iarspider can you please review it and eventually sign? Thanks.
@perrotta, @dpiparo, @rappoccio you are the release manager for this.
cms-bot commands are listed here

[cmsbuild]

-1

Failed Tests: UnitTests
Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-28bccf/28559/summary.html
COMMIT: c979f9e
CMSSW: CMSSW_12_6_X_2022-10-27-1100/el8_amd64_gcc10
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmsdist/8152/28559/install.sh to create a dev area with all the needed externals and cmssw changes.

Unit Tests

I found errors in the following unit tests:

---> test testSiStripHitEfficiency had ERRORS

Comparison Summary

Summary:

• No significant changes to the logs found
• Reco comparison results: 5 differences found in the comparisons
• DQMHistoTests: Total files compared: 48
• DQMHistoTests: Total histograms compared: 3384029
• DQMHistoTests: Total failures: 6
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 3384001
• DQMHistoTests: Total skipped: 22
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 47 files compared)
• Checked 201 log files, 48 edm output root files, 48 DQM output files
• TriggerResults: no differences found

[smuzaffar]

+externals

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_12_6_X/master IBs (but tests are reportedly failing). This pull request will now be reviewed by the release team before it's merged. @perrotta, @dpiparo, @rappoccio (and backports should be raised in the release meeting by the corresponding L2)