misc/ios,src/iostest.bash: support GOIOS_DEVICE_ID

When running multiple iOS builds on the same host, GOIOS_DEVICE_ID
is used to distinguish the devices. To improve support,

- Only restart the particular device when invoking iostest.bash
with the -restart flag.
- Make the exec wrapper lock file per-device.

For the iOS builder.

Change-Id: Id6f222981f25036399a43c3202a393dba89d87cb
Reviewed-on: https://go-review.googlesource.com/57970
Run-TryBot: Elias Naur <elias.naur@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

misc/ios/go_darwin_arm_exec.go

@@ -100,7 +100,7 @@ func main() {
 	//
 	// The lock file is never deleted, to avoid concurrent locks on distinct
 	// files with the same path.
-	lockName := filepath.Join(os.TempDir(), "go_darwin_arm_exec.lock")
+	lockName := filepath.Join(os.TempDir(), "go_darwin_arm_exec-"+deviceID+".lock")
 	lock, err = os.OpenFile(lockName, os.O_CREATE|os.O_RDONLY, 0666)
 	if err != nil {
 		log.Fatal(err)

src/iostest.bash

@@ -32,11 +32,15 @@ if [ "$1" = "-restart" ]; then
 	# Reboot to make sure previous runs do not interfere with the current run.
 	# It is reasonably easy for a bad program leave an iOS device in an
 	# almost unusable state.
-	idevicediagnostics restart
+	IDEVARGS=
+	if [ -n "$GOIOS_DEVICE_ID" ]; then
+		IDEVARGS="-u $GOIOS_DEVICE_ID"
+	fi
+	idevicediagnostics $IDEVARGS restart
 	# Initial sleep to make sure we are restarting before we start polling.
 	sleep 30
 	# Poll until the device has restarted.
-	until idevicediagnostics diagnostics; do
+	until idevicediagnostics $IDEVARGS diagnostics; do
 		# TODO(crawshaw): replace with a test app using go_darwin_arm_exec.
 		echo "waiting for idevice to come online"
 		sleep 10