Add `SwiftSynchronization_ SINGLE_THREADED_MODE` flag to use
empty mutex definition for certain apple platforms. This brings
Synchronization in line with the current build systems functionality
We will revisit this in the future to determine if we can add a mutex
definition for all Darwin platforms
Disable CMP0157 with the old driver as this breaks on Windows. Adjust
the Windows platform ID spelling to repair the Windows build. Take the
opportunity to re-order some of the structure so that it is similar to
the other modules.