CMP0103

Multiple calls to export() command with same FILE without APPEND is no longer allowed.

In CMake 3.17 and below, multiple calls to export() command with the same FILE without APPEND are accepted silently but only the last occurrence is taken into account during the generation.

The OLD behavior for this policy is to ignore the multiple occurrences of

export() command except the last one.

The NEW behavior of this policy is to raise an error on second call to export() command with same FILE without APPEND.

This policy was introduced in CMake version 3.18. CMake version 3.19.0-rc3 warns when the policy is not set and uses OLD behavior. Use the cmake_policy() command to set it to OLD or NEW explicitly.