go/build: add android to the flock

LGTM=minux
R=golang-codereviews, minux
CC=golang-codereviews
https://golang.org/cl/108450044

src/pkg/go/build/deps_test.go

@@ -360,7 +360,7 @@ func allowed(pkg string) map[string]bool {
 }
 
 var bools = []bool{false, true}
-var geese = []string{"darwin", "dragonfly", "freebsd", "linux", "nacl", "netbsd", "openbsd", "plan9", "solaris", "windows"}
+var geese = []string{"android", "darwin", "dragonfly", "freebsd", "linux", "nacl", "netbsd", "openbsd", "plan9", "solaris", "windows"}
 var goarches = []string{"386", "amd64", "arm"}
 
 type osPkg struct {