The use of PACKAGE_NAME for the project’s variable name is problematic, as this name is commonly used in CMake’s interface variables. If third-party CMake code handles with scopes improperly, our PACKAGE_NAME variable could end up with an unexpected value.
This PR avoids such conflicts by renaming all PACKAGE_* variables to CLIENT_*.
The code in the master branch works correctly only incidentally. It is definitely broken in #30997.