When installing two configurations of ITK on the same install folder, the ITKTarget*.cmake file of the first install is removed

Hi,

I want to create an installation of ITK with the debug and releaseWithDebInfo dll on the same folder, thanks to the CMAKE_DEBUG_POSTFIX. For this, I run two times the build and installation with the releaseWithDebInfo and debug build type, and the same install prefix folder.
However, I can notice in the second install, the following line:

```
-- Old export file "D:/.conan/8c8045/1/lib/cmake/ITK-5.0/ITKTargets.cmake" will be replaced. Removing files [D:/.conan/8c8045/1/lib/cmake/ITK-5.0/ITKTargets-relwithdebinfo.cmake].
-- Installing: D:/.conan/8c8045/1/lib/cmake/ITK-5.0/ITKTargets.cmake
-- Installing: D:/.conan/8c8045/1/lib/cmake/ITK-5.0/ITKTargets-debug.cmake
```

This is the first time I see an install script uninstalling cmake target files from a previous install.
Is it normal or is it a bug ?
If it is normal, how I am supposed to achieve an same installation for two configurations? Shall I merge myself the two installs and not use the same install prefix ?

I am building ITK 5.0.1, with cmake 3.16.5, on MSVC 16.5, Windows 10. Here is my cmake configuration:
BUILD_SHARED_LIBS=ON
CMAKE_DEBUG_POSTFIX="d"
BUILD_TESTING]=OFF
Module_RTK=ON
RTK_USE_CUDA=ON
RTK_BUILD_APPLICATIONS=OFF

Best regards,
Simon