CI uses older versions of the tools from Ubuntu 18.04. However, the more recent versions of the tools in Ubuntu 20.xx produce different formatting output, thus failing the CI.

CI:

# Ubuntu 18.04
clang-format version 8.0.0-3~ubuntu18.04.2 (tags/RELEASE_800/final)
Running cmake-format 0.6.5.

Latest Ubuntu:

# Ubuntu 20.04
clang-format version 8.0.1-9 (tags/RELEASE_801/final)
Running cmake-format 0.6.13.

This is a bit interesting, cause one using more recent version of the distro would unlikely be willing to downgrade their version, given that the same install_format_tools.sh is gonna deploy the more recent versions.

Morale: tools/format.sh can't be trusted if you are using latest Ubuntu.