Fix cmake install (!103)

## What is the bug
CMake install prefix using `${CMAKE_INSTALL_PREFIX}` does not take environmental install path, but rather hardcoded to the explicit path. See [Sergey's comment](!95 (comment 280056)

)
## How do you fix it
Use `$<INSTALL_PREFIX>` instead.

Approved-by: Sergey Kosukhin <sergey.kosukhin@mpimet.mpg.de>
Merged-by: Yen-Chen Chen <yen-chen.chen@kit.edu>
Changelog: bugfix