This brings the semantics a little closer to the Go tool. I find it surprisingly useful for testing if android-specific changes to a package compile. Change-Id: I9f5730f678eb418fc5659fa82c1fe9b78a084e33 Reviewed-on: https://go-review.googlesource.com/5741 Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>