cmake: Pass path list in a Windows friendly way

When invoking cmake/llext-edk.cmake, CMakeLists.txt was sending the list
of includes as a colon separated list. On Windows, this list was
actually a single item, so it wasn't being parsed properly.

This patch sends the list as a cmake list and uses separate_arguments()
on the receiving side to fix it.

Fixes #73069

Signed-off-by: Ederson de Souza <ederson.desouza@intel.com>