Re-org the merge_zips logiic under Turbine rule.

Mac java build has flaky error for merge_zips. The error happend is
because both turbine.jar.premerged and static_java_libs are missing.

We allow one of them can be missing, but we don't allow both of them are
missing. So re-org the merge_zips logic to see if the input of Turbine is
empty or it is due to Turbine internal.

Bug: b/66441248
Test: m clean && m -j32
Change-Id: I3c4b15004fd67fef2b83eabc36841bc8c8ff6e4c