Cmake errors: Unknown CMake command "add_subdirectory_ifdef"

[lcj]

I am trying to use some examples to add a drivers directory on my project. While doing so I run into build errors which seem to indicate a toolchain problem. The two errors were:

Unknown CMake command "add_subdirectory_ifdef".

and 

CMake Error at drivers/display/gc9a01/CMakeLists.txt:1 (zephyr_sources):

  Unknown CMake command "zephyr_sources".

it seems like zephyr_sources and add_subdirectory_ifdef are not supported.

[lcj]

I found the problem. It was the order of the subdirectory call in the parent CMakeLists.txt. I moved it down and resolved the issue. In the sample there was no subdirectory to process so I didn't know where to put it.