The Windows Visual Studio build rebuilds src/third_party/js-1.7/jsscan.c on every build of mongod.exe, mongos.exe, mongo.exe or test.exe, forcing a relink each time. Linking release builds takes forever, so this is really annoying. The problem is that we are unconditionally running jskwgen.exe to create jsautokw.h before starting the mongo

rebuild; we do this in a Pre-build step. This pre-build step should only recreate jsautokw.h when it is out-of-date, which will be "never" after it's been built once. Some custom JScript code should be able to do this test.