Compile CFLite requires some unknown dependencies
You can find the files you need in the libdispatch-442.1.4 download at the open source site you linked above.

And libdispatch is included with 10.11.5 as well, as you can see on this page. https://opensource.apple.com/release/os-x-10115/

I don't have a Mac here to confirm, but I assume if you haven't installed Xcode (with its accompanying SDKs) then the headers won't be installed on your Mac.