NET9 SDK copies (new) file for transitive dependency

> [!NOTE]
> Note this is for `DisableTransitiveProjectReferences=true`

After upgrading to net9, a new file `staticwebassets.build.endpoints.json` is copied from a transitive dependency.

### To Reproduce
```
git clone https://github.com/AndyGerlicher/staticwebassetsrepro.git
cd staticwebassetsrepro
powershell .\build.ps1
```
### Expected Result
When `DisableTransitiveProjectReferences=true` and `BuildProjectReference=false`, content from a transitive dependency should not be copied.

### Further details
This causes issues for build systems that monitor file access and prevent access to non-dependencies. A significant number of repos (MS internal) will have to add unnecessary references to upgrade to net9 SDK (even when **NOT** targeting net9).