Windows Phone lacks the old CreateThread/beginthreadex APIs for
creating threads. (Technically, the functions still do exist,
but they aren't officially supported and aren't visible in the
headers when targeting Windows Phone.)
Building code that uses the Windows Runtime language extensions
requires building with the -ZW option.
This requires using the external gas-preprocessor tool that
converts the gnu assembler format sources to armasm format at
build time. This allows keeping the source files in one single
format but only converting while building.