CMake tries to use system Python instead of LCG if version is higher

The way LHCb uses to hint CMake to find the version of Python from the LCG toolchain does not work if there's a higher version of Python in the PATH.

This is because we are using the Python_FIND_STRATEGY VERSION instead of LOCATION, see https://cmake.org/cmake/help/latest/module/FindPython.html#hints

/cc @bcouturi