Export AlarmManagerService as a filegroup

ARCVM needs to replace the file replaced by product_variable.arc back to
the original version. By exporting this original version, ARCVM can
pick it up and use it.

Bug: 135558634
Test: Compile bertha and cheets, and manually check the conditional.
Change-Id: I1bb2bd5f631d9f9a3271c1f5672da181785ca289
Merged-In: I1bb2bd5f631d9f9a3271c1f5672da181785ca289