change gen-version dirty check
change gen-version dirty check

The current check uses update-index, which doesn't work if .git is read-only

JackieXie168/rethinkdb,grandquista/rethinkdb,JackieXie168/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,grandquista/rethinkdb,JackieXie168/rethinkdb,JackieXie168/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,grandquista/rethinkdb,JackieXie168/rethinkdb