[cmake-developers] Adding Swift support to CMake for Linux/Makefiles

[Eric Wing]

> For the moment, I like swiftc over swift because it seems a lot
> simpler. I hope this means the least changes for CMake right now.

I need to correct myself on this. While I like swiftc for looking
simpler, I'm actually thinking swift might be fewer changes since the
file-by-file thing is what CMake does today.
It may turn out swift is easier to figure out in the end too when we
eventually look at add_library and linking them (since we can reverse
engineer from the Xcode logs).

But either way, both of them seem to need SOURCES.

Thanks,
Eric