Fix Centos CI build

Summary

This merge request fixes the CentOS CI build.

Implementation details

Centos CI builds were broken for several reasons :

• The runners have been updated to Debian 10, this was causing this bug : https://gitlab.orfeo-toolbox.org/orfeotoolbox/otb/-/jobs/26223. The logs don't give a lot of information, but the Centos docker container is not created correctly. @sdinot solved the problem by downgrading the runner to Debian 9. We are not sure of the cause of the bug, maybe the kernels differences between Debian 10 and Centos 6.6 are too important.
• we had to re-generate the docker images for centos 6 builds, centos-base and centos-superbuild-base. However the image builds failed because :
  • devtoolset-6 is not available in yum anymore (it was deprecated) see this CI job. The dockerfile has been modified to use devtoolset-7.
  • rh-git29 (git version 2.9) is not available in centos-release-scl. See this job. I'm not sure why, note that the git package from yum official repo is not used because the version is too low (1.7) for git-lfs. The solution chosed is to compile git from sources in the dockerfile. Another solution would have been to use another repo, but I could not find an official repo with a recent git and didn't want to use an unofficial one.
• In the packaging step, when recursively looking at which dynamic library should be packaged, it appears that we need to package libgssapi_krb5 see this log . However this is a system library, available on the base Centos 6.6 image, and it is not in the search path of otb when looking for libraries to package. The solution is to add libgssapi_krb5 to the list of possible system libraries for Linux packages. However I don't understant why this problem was not present in old centos CI builds, but this is hard to test now...

This Merge Request only concerns the last point of this list. See the otb-build-env project for the docker related changes.

Copyright

The copyright owner is CNES and has signed the ORFEO ToolBox Contributor License Agreement.

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Check before merging:

• All discussions are resolved
• At least 2 votes from core developers, no vote.
• The feature branch is (reasonably) up-to-date with the base branch
• Dashboard is green
• Copyright owner has signed the ORFEO ToolBox Contributor License Agreement
• Optionally, run git diff develop... -U0 --no-color | clang-format-diff.py -p1 -i on latest changes and commit