ninja windows: fix pdb name fom r1301
ninja windows: fix pdb name fom r1301

And add assert to WriteVariableList because I seem to do that every time I use
it.

R=thakis@chromium.org

Review URL: https://chromiumcodereview.appspot.com/9950140
old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google