CMP0047

Use QCC compiler id for the qcc drivers on QNX.

CMake 3.0 and above recognize that the QNX qcc compiler driver is different from the GNU compiler. CMake now prefers to present this to projects by setting the CMAKE_<LANG>_COMPILER_ID variable to QCC instead of GNU. However, existing projects may assume the compiler id for QNX qcc is just GNU as it was in CMake versions prior to 3.0. Therefore this policy determines for QNX qcc which compiler id to report in the CMAKE_<LANG>_COMPILER_ID variable after language <LANG> is enabled by the project() or enable_language() command. The policy must be set prior to the invocation of either command.

The OLD behavior for this policy is to use the GNU compiler id for the qcc and QCC compiler drivers. The NEW behavior for this policy is to use the QCC compiler id for those drivers.

This policy was introduced in CMake version 3.0. Use the cmake_policy() command to set this policy to OLD or NEW explicitly. Unlike most policies, CMake version 3.17.5 does not warn by default when this policy is not set and simply uses OLD behavior. See documentation of the CMAKE_POLICY_WARNING_CMP0047 variable to control the warning.