L1(Topo) Installation Fixes, master branch (2020.04.03.)

Made the L1 packages install themselves correctly in case of build failures. This way in case the file generation commands in them fail for some reason, the nightly will not be prevented from installing fully.

I ran into these imperfections while working on !31741 (merged), and not being able to properly install (with make install/fast) the configured release for testing purposes, without building it first.

Note that I also made some additional cleanups in the code while at it:

• The whole "release recompilation" concept was abandoned a very long time ago in AtlasCMake. So I removed remnants of it from these packages.
• Updated the commands to use the built-in CMake variables/commands a little better. (For a better platform independence...)