cmake: fix out of tree hal build fail
cmake: fix out of tree hal build fail

Fix out of tree building hal fail with different drive on windows.

Signed-off-by: Jim Tan <bc3afe8b929036c6fe07f34e95d1cf431d146197@ite.com.tw>

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