The gomobile tool mishandled build tags in two ways, first by
ignoring tags for iOS, second by passing multiple tags along to
the go tool incorrectly. This CL fixes both.
Fixesgolang/go#18523Fixesgolang/go#18515
Change-Id: I28a49c1e23670adb085617d9f5fb5cd5e22a4b65
Reviewed-on: https://go-review.googlesource.com/34955
Reviewed-by: David Crawshaw <crawshaw@golang.org>