CMake version bump

We currently have a requirement of cmake version 3.9 for the project.

However, we have (at least one) commands that require a higher version. This call to ECHO_OUTPUT_VARIABLE requires at least cmake version 3.18

I think this has been so-far missed because this command is only in the FLUKA cmake file, which the CI doesn't cover.

To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information