CMake Error at NonValidTarget-C_COMPILER_FRONTEND_VARIANT\.cmake:1 \(add_custom_command\):
  Error evaluating generator expression:

    \$<C_COMPILER_FRONTEND_VARIANT>

  \$<C_COMPILER_FRONTEND_VARIANT> may only be used with binary targets\.  It
  may not be used with add_custom_command or add_custom_target\.
Call Stack \(most recent call first\):
  CMakeLists\.txt:[0-9]+ \(include\)
