misc/ios: add missing CGO_ENABLED=1 for running standalone tests

Change-Id: Icfd5b9d1ca757081af7885189ae7094fa1b3d8f1
Reviewed-on: https://go-review.googlesource.com/c/go/+/182377
Run-TryBot: Elias Naur <mail@eliasnaur.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

misc/ios/README

@@ -40,7 +40,7 @@ To use the go tool directly to run programs and tests, put $GOROOT/bin into PATH
 the go_darwin_$GOARCH_exec wrapper is found. For example, to run the archive/tar tests
 
 	export PATH=$GOROOT/bin:$PATH
-	GOARCH=arm64 go test archive/tar
+	GOARCH=arm64 CGO_ENABLED=1 go test archive/tar
 
 Note that the go_darwin_$GOARCH_exec wrapper uninstalls any existing app identified by
 the bundle id before installing a new app. If the uninstalled app is the last app by