[BuildRules] Support using -isystem instead of -I for system tools

[smuzaffar]

We get a lot of warnings coming from externals e.g. tbb, boost. New build rules allows to use -isystemINCLUDE_DIR instead of -IINCLUDE_DIR` which can instruct compiler to ignore warnings coming from headers under INCLUDE_DIR.

An external tool can set following flag to declare its include as system includes.

<flags SYSTEM_INCLUDE="1"/>

[smuzaffar]

please test

[cmsbuild]

The tests are being triggered in jenkins.
https://cmssdt.cern.ch/jenkins/job/ib-run-pr-tests/6992/console Started: 2020/06/12 16:02

[cmsbuild]

A new Pull Request was created by @smuzaffar (Malik Shahzad Muzaffar) for branch IB/CMSSW_11_2_X/master.

@cmsbuild, @smuzaffar, @mrodozov, @tulamor can you please review it and eventually sign? Thanks.
cms-bot commands are listed here

[cmsbuild]

+1
Tested at: 2261d03
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-491097/6992/summary.html
CMSSW: CMSSW_11_2_X_2020-06-12-1100
SCRAM_ARCH: slc7_amd64_gcc820

[cmsbuild]

Comparison job queued.

[smuzaffar]

+externals

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_11_2_X/master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @silviodonato, @dpiparo (and backports should be raised in the release meeting by the corresponding L2)

[cmsbuild]

Comparison is ready
https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-491097/6992/summary.html

Comparison Summary:

• No significant changes to the logs found
• Reco comparison results: 0 differences found in the comparisons
• DQMHistoTests: Total files compared: 36
• DQMHistoTests: Total histograms compared: 2778811
• DQMHistoTests: Total failures: 1
• DQMHistoTests: Total nulls: 0
• DQMHistoTests: Total successes: 2778760
• DQMHistoTests: Total skipped: 50
• DQMHistoTests: Total Missing objects: 0
• DQMHistoSizes: Histogram memory added: 0.0 KiB( 35 files compared)
• Checked 152 log files, 16 edm output root files, 36 DQM output files