cmocka is not OPTIONAL dependency

trying to build libssh without cmocka installed outputs the following cmake error:

CMake Error at /usr/local/share/cmake-3.30/Modules/FindPackageHandleStandardArgs.cmake:233 (message):
  Could NOT find CMocka (missing: CMOCKA_LIBRARIES CMOCKA_INCLUDE_DIR)
Call Stack (most recent call first):
  /usr/local/share/cmake-3.30/Modules/FindPackageHandleStandardArgs.cmake:603 (_FPHSA_FAILURE_MESSAGE)
  cmake/Modules/FindCMocka.cmake:63 (find_package_handle_standard_args)
  CMakeLists.txt:59 (find_package)

The problem is easily fixed by installing cmocka: sudo apt-get install libcmocka-dev