cxxmodules: Incorrect object filename from $<TARGET_OBJECTS:tgt> with MSVC
The value returned from `$<TARGET_OBJECTS:tgt>` is incorrect when compiling an object library consisting of only a C++ module with MSVC.
This causes issues with linking module libraries since the obj file of the target library will have an unexpected name.
# Minimal reproduction:
[CMakeLists.txt](/uploads/091b7ed63583e5b3451c9e6cf40bb191/CMakeLists.txt)
[foo.ixx](/uploads/847c47239795ad8a8b6c682baebd983f/foo.ixx)
# System info
Visual Studio 17 2022
MSVC 19.40.33521.0
MSBuild version 17.10.0-preview-24081-01+97651a25d for .NET Framework
CMake version 3.29.0-rc2
issue