Specify libdir for libunwind

[mrodozov]

Resolves: cms-sw/cmssw#33668

[cmsbuild]

A new Pull Request was created by @mrodozov (Mircho Rodozov) for branch IB/CMSSW_12_0_X/master.

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

[mrodozov]

test parameters:

• architecture = slc7_ppc64le_gcc9
• addpkg = FWCore/Framework

[mrodozov]

please test

[cmsbuild]

+1

Summary: https://cmssdt.cern.ch/SDT/jenkins-artifacts/pull-request-integration/PR-b64823/14977/summary.html
COMMIT: eb42007
CMSSW: CMSSW_12_0_X_2021-05-09-2300/slc7_ppc64le_gcc9
User test area: For local testing, you can use /cvmfs/cms-ci.cern.ch/week0/cms-sw/cmsdist/6886/14977/install.sh to create a dev area with all the needed externals and cmssw changes.

[mrodozov]

+externals

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next IB/CMSSW_12_0_X/master IBs (tests are also fine). This pull request will now be reviewed by the release team before it's merged. @silviodonato, @dpiparo, @qliphy (and backports should be raised in the release meeting by the corresponding L2)