LCG_87 Downgrade, 21.0-mc16a branch (2020.11.30.)

Switched the build of Athena (back) to LCG_87.

As discussed on ATLINFR-3850, using LCG_88 in this branch was quite a big mistake. So this is a first step needed in making the x86_64-centos7-gcc62-opt build of this branch functional.

added bugfix label

This merge request affects no known packages. Consult an expert!

This merge request affects 1 file:

• Build/AtlasBuildScripts/build_atlasexternals.sh

Could not map the following files to a domain:

• Build/AtlasBuildScripts/build_atlasexternals.sh

Adding @akraszna as watcher

added 21.0-mc16a no-domain review-pending-level-1 labels

CI Result SUCCESS (hash 27d513ba)

	Athena
externals
cmake
make
required tests
optional tests	N/A

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 296
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 45314]

Hi @rmazini,

Could you merge this one please? See ATLINFR-3850 for all the details.

Cheers,

John

Clear, approving for fast merging....

Pavol [as L2 MR shifter]

added review-approved label and removed review-pending-level-1 label

Thanks @pavol!

merged

mentioned in commit 1476a62a

Thanks @rmazini.