Shard kythe invocations when javac is sharded

The kythe pipeline has trouble injesting all 6000 files of
framework.jar at once.  Shared invocations of the kythe extractor
when javac is sharded to produce multiple smaller kzip files.

Bug: 140426870
Test: no change to build.ninja
Test: m out/soong/.intermediates/frameworks/base/framework/android_common/framework0.kzip
Test: TestSharding in java_test.go
Change-Id: I867db4ef5cb1e7f3ce8359a46aac2c00ed8a8912