Add sourcepath to inputs of remoteable metalava action.

Test: presubmit
Change-Id: Idd77abddac0a676302226eb62883c74d5d7489af
diff --git a/java/droiddoc.go b/java/droiddoc.go
index 879353d..5f5dfa1 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -1388,6 +1388,7 @@
 			pool = v
 		}
 		inputs := []string{android.PathForOutput(ctx, "host", ctx.Config().PrebuiltOS(), "framework", "metalava.jar").String()}
+		inputs = append(inputs, sourcepaths.Strings()...)
 		if v := ctx.Config().Getenv("RBE_METALAVA_INPUTS"); v != "" {
 			inputs = append(inputs, strings.Split(v, ",")...)
 		}