cmake: extensions: fix zephyr_dt_preprocess() CPP handling

This option argument needs to be able to accept a list of arguments.
One use case is the way CMAKE_DTS_PREPROCESSOR is set in
cmake/compiler/armclang/generic.cmake.

Reported-by: Kumar Gala <kumar.gala@intel.com>
Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
1 file changed