Fix preprocessor integration when using along MSBuild

[AeroStun]

Fix the spurious errors, and transform/filter the flags from MS -> GNU format (well, keep only the defines, incdirs, and force-includes)

[AeroStun]

I guess MSBuild does not like error being printed to stderr, because it sure fails the custom build task of sketch generation whenever non-fatal errors are printed by arduino-prelude.
The quickfix is to grab Ninja on-the-fly like we do arduino-prelude; the correct fix is to find out how to make MSBuild not suck