Please don't arbitrarily assume a specific schema for the `PYTHONPATH`

[wucke13]

This line arbitrarily assumes that only two valid directories make up the python path. That is a wrong assumption, i.e. it causes the build failure in https://github.com/DLR-FT/seL4-nix-utils/blob/958f2df5e9568af025d21a80fd4fb7b65ed4d2f1/pkgs/seL4-test.nix ; a correct PYTHONPATH (consisting of more than two directories...) is assembled, only to be discarded/overridden by the cmake script.

camkes-tool/camkes.cmake

Line 299 in 9c7c211

set(CAMKES_TOOL_ENVIRONMENT "PYTHONPATH=${CAMKES_TOOL_DIR}:${PYTHON_CAPDL_PATH}")

i would much prefer if either the PYTHONPATHis let be just as is (do python dependency management patterns really need to be enforced by cmake scripts?) or to prefix it, but leaving remaining elements on the path.