Testing cmake support on Windows

I am not set up to test the cmake support on Windows but would ask whoever does this take the same approach that I used in constructing these committed files. Start with the printout of the stock…

make compiler=clang

build on Windows (which I assume works) and modify runtime/src/CMakeLists.txt to match the exact flags used and source files compiled by build.pl on Windows (wrapping these with the appropriate conditionals to leave the linux/darwin builds unchanged).