Don’t use CMAKE_SYSTEM

It makes the build unreproducible, see https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/biboumi.html And also biboumi reports the version where it was built, not the version of the running OS.

Use uname(2) instead.

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