[CMake] Unity builds vs. compile_commands.json

[Brad King]

On 10/10/19 6:53 PM, Paul Smith wrote:
> Is there an intent to address this before the 3.16 release?  
> 
> Or is this a known limitation, which may or may not be addressed in
> some future version of CMake?
> 
> If the latter it should probably be added to the release notes and/or
> documentation for unity builds.

I've opened an issue for it:

* https://gitlab.kitware.com/cmake/cmake/issues/19826

This won't block the release so I've updated the documentation to
mention this limitation.

-Brad