cmd/gomobile: remove redundant build

The extra build can't be required, because it is not run for the
build of the first GOARCH later in the loop. Tests run fine
without it.

Change-Id: Ida27e31ace2417192cce06c2efc93fa0d357012e
Reviewed-on: https://go-review.googlesource.com/98975
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

cmd/gomobile/bind_androidapp.go

@@ -44,9 +44,6 @@ func goAndroidBind(pkgs []*build.Package, androidArchs []string) error {
 		toolchain := ndk.Toolchain(arch)
 
 		if !first {
-			if err := goInstall(paths, env, androidArgs...); err != nil {
-				return err
-			}
 			err := goBuild(
 				mainFile,
 				env,