[CMake] scope of set_source_files_properties?

[Brad King]

Simmons, Aaron wrote:
> Lots of these subfolders have per-source flags/args
> 
> Is there some other way to go about doing this?

Generally per-source flags should be reserved for tweaking and
workarounds such as using -O0 to disable buggy optimizations.
Their Makefile and VS project file implementations are not
scalable (as in changing one flag on one file causes the whole
target to recompile).

Are all these sources going into a single executable?
If so, I suggest using an add_library() to create a static
library for each feature.  Then link the executable to all
of them.

-Brad