Help: Improve readability and fix inaccuracies in unity build docs
Apart from general readability, structure and formatting improvements, the following are addressed by these changes:
- The default value for the batch size is set in the
UNITY_BUILD_BATCH_SIZEproperty itself, not the
CMAKE_UNITY_BUILD_BATCH_SIZEvariable (the variable has no default value).
- Stronger wording highlighting that projects should not turn on unity builds, it needs to be under developer control.
- Examples used for code before/after includes are slightly expanded and are safer (makes no assumptions about what the included sources might do with
I also removed the note about the
HEADER_FILE_ONLY implementation detail. We don't need to mention this and it will have to be addressed anyway, as highlighted in #19946 (closed).