Added a build target for cityhash.
Added a build target for cityhash.

google/gjstest,okdave/gjstest,google/gjstest,aungzanbaw/gjstest,okdave/gjstest,google/gjstest,okdave/gjstest,aungzanbaw/gjstest,google/gjstest,aungzanbaw/gjstest,okdave/gjstest,aungzanbaw/gjstest