Fix `go vet` issues

Test: go vet ./...
Change-Id: Ifb936ccc5e2b5a2c3fcbbbcb54f680e2973ea1b3
diff --git a/cmd/soong_ui/main.go b/cmd/soong_ui/main.go
index 47682ff..b603571 100644
--- a/cmd/soong_ui/main.go
+++ b/cmd/soong_ui/main.go
@@ -84,7 +84,7 @@
 		stat.Finish()
 	})
 
-	buildCtx := build.Context{&build.ContextImpl{
+	buildCtx := build.Context{ContextImpl: &build.ContextImpl{
 		Context: ctx,
 		Logger:  log,
 		Tracer:  trace,