When using full paths to source xaml files, the generated .g.cs files aren't placed in subfolders in the obj\target folder

**Version Used**: Microsoft (R) Visual C# Compiler version 4.0.1-1.21568.1 (6ab66011)

**Steps to Reproduce**:

1. Create a .csproj. Using full pathnames, specify multiple xaml files with the same name, but a different subfolder.
```

Views\View1\GeneralView.xaml
Designer


Views\View2\GeneralView.xaml
Designer

```
2. Build
3. Build Fails. Observe CS2002 warnings, combined with other errors because only the _last_ `GeneralView.g.cs` file was written to `/obj/x64/Debug`

**Expected Behavior**:
Each `GeneralView.g.cs` file should be in a subfolder in the object folder.
`/obj/x64/Debug/Views/View1/GeneralView.g.cs`
`/obj/x64/Debug/Views/View2/GeneralView.g.cs`

**Actual Behavior**:
Each `GeneralView.g.cs` file overwrites the previous file in the root object folder, so you end up with only the _last_ one in the root object folder: `/obj/x64/Debug/GeneralView.g.cs`

**Notes**:
The distinction is that the csproj file is using full paths to the source files, instead of relative paths. I'm using `cmake` in my project, and it generated the csproj files like this. I would file a bug with `cmake`, but there doesn't seem to be anything in the specification for csproj files that would preclude using full paths to source files.