Export of CMAKE_COMMAND

[MBirn]

Exporting CMAKE_COMMAND in build-all.sh and using it throughout the scripts seems wrong to me.

All other build scripts write their own module files and assume the modules of dependencies to be loaded before their invocation.

Is it possible to remove that and rely on the user to prepare their build environment?

[diehlpk]

@MBirn I will work on that improvement soon.