When built with output enabled, sometimes a few lines would be
interchanged, depending on the order in which parallel tasks
complete. Simplify the dispatcher logic a bit to ensure we get
the same output ordering every time.
This does not impact the running time of the benchmark.
This means that we can now edit benchmarks in Xcode! Keep in mind:
1. This is not an official build. It is just so we can use Xcode to edit files
and get IDE features.
2. I had to do a little hackery to keep the build the way it is today where all
single-source files are their own modules.
3. As long as we do not change the directory structure, everything should just
update and work since I added a little code that dynamically adds the tests.
Also, to do this I had to rename multi-source/PrimsSplit/main.swift =>
Prims_main.swift. That is because the name main.swift is special in some way and
I hit linker errors. By simply changing the name from main.swift =>
Prims_main.swift, everything is good. I am going to file a separate bug for
that.
