Disable ResourceProcessorBusyBox in kythe builds

ResourceProcessorBusyBox generates the R.jar binary from R.txt without
creating an intermediate R.srcjar file. Disable this behavior in kythe
builds (ctx.Config().EmitXrefRules()) to support xrefs to R imports

Test: XREF_CORPUS=$internal_corpus m nothing
Test: aninja -t query out/soong/.intermediates/frameworks/libs/systemui/animationlib/animationlib_tests/android_common/animationlib_tests.kzip
Test: verified that an R.srcjar is present in its deps

Bug: 354854007
Change-Id: I2d63c3393c5bc58103c267c4593172ce77fbc79c