cmake: support build info in Zephyr

Store informations regarding the current Zephyr build.
The following informations are stored during CMake configure:
- Board information
- Application source directory
- Application configuration directory
- Toolchain information
- Devicetree files
- Kconfig config files
- Zephyr version

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