Different CMAKE_BUILD_TYPES must not overwrite the *-targets.cmake files and the libs

[ClausKlein]

A valid install cmake config package looks like this:

stagedir/lib/
|-- cmake
|   `-- my_package
|       |-- cxx-modules-my_package-targets-Debug.cmake
|       |-- cxx-modules-my_package-targets-Release.cmake
|       |-- cxx-modules-my_package-targets.cmake
|       |-- my_package-config-version.cmake
|       |-- my_package-config.cmake
|       |-- my_package-targets-debug.cmake
|       |-- my_package-targets-release.cmake
|       |-- my_package-targets.cmake
|       |-- src
|       |   `-- algo-interface.cppm
|       |-- target-Algo-Debug.cmake
|       `-- target-Algo-Release.cmake
|-- libAlgo.dylib
`-- libAlgoD.dylib

4 directories, 13 files