This updates our compilers, gn and ninja. Also, we now explicitly specify the buildtools artifacts we actually use instead of downloading everything from the catalog.
The build error was due to unused lambda captures being reported as warnings (which we turn into errors).
* Partially port FML to Windows.
* Adds a message loop impl for Windows
* Ports `thread.cc` to Windows
All FML unittests are now passing on Windows.
FML as a whole does not compile on windows yet because `mapping.cc` imports `sys/mman.h`, which is not available on Windows and the replacement API for memory-mapped files is very different on Windows, see https://msdn.microsoft.com/en-us/library/windows/desktop/aa366556%28v=vs.85%29.aspx.
* update licenses
* review comments
