Pass the common sources rsp file as `--common_srcs` to extractor

This additional metadata allows the indexer to differentiate between
platform specific and platform agnostic kotlin code.

Bug: 3266381
Test: ran the indexer on `kotlinx_serialization_core` java_library
Change-Id: I860552808198cafa95fe0d5b6faa725b985e24d0
diff --git a/java/kotlin.go b/java/kotlin.go
index 79781a0..3573f1e 100644
--- a/java/kotlin.go
+++ b/java/kotlin.go
@@ -163,7 +163,7 @@
 			"srcJarDir":       android.PathForModuleOut(ctx, "kotlinc", "srcJars.xref").String(),
 		}
 		if commonSrcsList.Valid() {
-			args["commonSrcFilesList"] = "--srcs @" + commonSrcsList.String()
+			args["commonSrcFilesList"] = "--common_srcs @" + commonSrcsList.String()
 		}
 		ctx.Build(pctx, android.BuildParams{
 			Rule:        kotlinKytheExtract,