Fix `go vet` issues

Test: go vet ./...
Change-Id: Ifb936ccc5e2b5a2c3fcbbbcb54f680e2973ea1b3
diff --git a/java/java.go b/java/java.go
index 99af2f5..53f851b 100644
--- a/java/java.go
+++ b/java/java.go
@@ -574,7 +574,7 @@
 	ctx.AddDependency(ctx.Module(), libTag, j.properties.Libs...)
 	ctx.AddDependency(ctx.Module(), staticLibTag, j.properties.Static_libs...)
 	ctx.AddFarVariationDependencies([]blueprint.Variation{
-		{"arch", ctx.Config().BuildOsCommonVariant},
+		{Mutator: "arch", Variation: ctx.Config().BuildOsCommonVariant},
 	}, annoTag, j.properties.Annotation_processors...)
 	android.ExtractSourcesDeps(ctx, j.properties.Srcs)
 	android.ExtractSourcesDeps(ctx, j.properties.Exclude_srcs)