cmake: ensure zephyr_module.py creates posix path output for cmake
cmake: ensure zephyr_module.py creates posix path output for cmake

This commit fixes an issue in windows where zephyr_modules.txt contains
a \ as path separator.
This causes issues later when using the path generated by
zephyr_module.txt are used as variables in CMake on windows.

Signed-off-by: Torsten Rasmussen <a7c5b1d5a1f41fce6edfa3f7c2392ae0c59deafe@nordicsemi.no>

zephyrproject-rtos/zephyr,finikorg/zephyr,finikorg/zephyr,nashif/zephyr,galak/zephyr,Vudentz/zephyr,galak/zephyr,nashif/zephyr,galak/zephyr,nashif/zephyr,Vudentz/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,Vudentz/zephyr,Vudentz/zephyr