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

java/builder.go

@@ -229,10 +229,9 @@ func RunErrorProne(ctx android.ModuleContext, outputFile android.WritablePath,
 
 // Emits the rule to generate Xref input file (.kzip file) for the given set of source files and source jars
 // to compile with given set of builder flags, etc.
-func emitXrefRule(ctx android.ModuleContext, xrefFile android.WritablePath,
+func emitXrefRule(ctx android.ModuleContext, xrefFile android.WritablePath, idx int,
 	srcFiles, srcJars android.Paths,
-	flags javaBuilderFlags, deps android.Paths,
-	intermediatesDir string) {
+	flags javaBuilderFlags, deps android.Paths) {
 
 	deps = append(deps, srcJars...)
 
@@ -260,6 +259,11 @@ func emitXrefRule(ctx android.ModuleContext, xrefFile android.WritablePath,
 		processor = "-processor " + flags.processor
 	}
 
+	intermediatesDir := "xref"
+	if idx >= 0 {
+		intermediatesDir += strconv.Itoa(idx)
+	}
+
 	ctx.Build(pctx,
 		android.BuildParams{
 			Rule:        kytheExtract,