Made the Windows "Dart Run" build use checked mode.

Default behavior in the Dart Editor is to run in checked mode, and I'd like to run it from Sublime in checked mode as well. Added `-c` the parameter to the build system.
Totally thought about that, but I was just copying what the Linux build system was already doing. Shall I change the Linux version to `--checked` as well? I don't have a Linux box that I can test it on though...