Ninja Compatibility Updates, master branch (2020.12.14.)

These are some updates for making it more convenient to use Ninja as the build system in ATLAS CMake projects.

The CPack configuration in AtlasCMake is updated to work with any CMake generator, and at the same time to allow for the cpack executable to be called from outside of the build directory.

The update in CLHEP is just to not force the usage of GNU Make for that external when the rest of the build uses Ninja. (Whatever the reason was for forcing the usage of GNU Make in the past, it doesn't seem to be present anymore.)

AE Build SUCCESS
Build logfiles are available at Jenkins [AE-MERGE-REQUEST-CC7 #417]

mentioned in commit 1a5c5088

merged

mentioned in merge request !799 (merged)