cmake: locate Zephyr SDK before locating other host tools.

Follow-up: #49672

Zephyr SDK and host tools detection was reworked in #49672.

That rework accidentally changed the lookup order from:
- Zephyr SDK
- Other host tools
- Generic (host) C compiler

into
- Other host tools
- Zephyr SDK
- Generic (host) C compiler

this causes host tools shipped with Zephyr SDK, such as openocd to not
be discovered unless in path.

Restore the original order so that Zephyr SDK is located first so that
host tools from the SDK can be found without having them in path.

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