Fix build break caused by registering genrules twice

Two separate changes that passed presubmits separately and did not
conflict when merged together unfortunately clashed at runtime. The
changes are:
* Ic00c7e480dc738d7a88d038aca6ab95a1502a24a
* Ic98fdc29a63155174a3227e7e918b26f0a8763bb

Test: m nothing
Change-Id: I7b5704c22cc2ea2095f5fb92c59f0526bb445f13