Error on relative include with generator expression.
Diagnostics in CMake 2.8.12 and lower silently ignored an entry in the :prop_tgt:INTERFACE_INCLUDE_DIRECTORIES of a target if it contained a generator expression at any position.
The path entries in that target property should not be relative. High-level API should ensure that by adding either a source directory or a install directory prefix, as appropriate.
As an additional diagnostic, the :prop_tgt:INTERFACE_INCLUDE_DIRECTORIES generated on an :prop_tgt:IMPORTED target for the install location should not contain paths in the source directory or the build directory.
The OLD behavior for this policy is to ignore relative path entries if they contain a generator expression. The NEW behavior for this policy is to report an error if a generator expression appears in another location and the path is relative.
This policy was introduced in CMake version 3.0. CMake version |release| warns when the policy is not set and uses OLD behavior. Use the cmake_policy command to set it to OLD or NEW explicitly.