Using 'go' command in tests is confusing when using a different version of Go (e.g., go1.13rc1). Use GOROOT/bin/go so that the same Go is used. Change-Id: I0ca297207acc5e7fd8b291f544302f6c7b0d38e1 Reviewed-on: https://go-review.googlesource.com/c/mobile/+/191517 Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com> Run-TryBot: Hyang-Ah Hana Kim <hyangah@gmail.com>