sensorlog: make gosh.BuildGoPkg a package-level helper

Also updates v23test's BuildGoPkg to be package-level.

MultiPart: 6/6

Change-Id: I37cc414f2c8211298021e37b22196fe93b2985b5
diff --git a/go/src/v.io/x/sensorlog/internal/client/device_v23_test.go b/go/src/v.io/x/sensorlog/internal/client/device_v23_test.go
index 9fdafed..2c22bd7 100644
--- a/go/src/v.io/x/sensorlog/internal/client/device_v23_test.go
+++ b/go/src/v.io/x/sensorlog/internal/client/device_v23_test.go
@@ -161,7 +161,7 @@
 }
 
 func startAdditionalMT(sh *v23test.Shell, args ...string) (string, func(sig os.Signal)) {
-	mounttabledPath := sh.BuildGoPkg("v.io/x/ref/services/mounttable/mounttabled")
+	mounttabledPath := v23test.BuildGoPkg(sh, "v.io/x/ref/services/mounttable/mounttabled")
 	inv := sh.Cmd(mounttabledPath, args...)
 	inv.Start()
 	return inv.S.ExpectVar("NAME"), inv.Terminate
diff --git a/go/src/v.io/x/sensorlog/internal/client/measured_v23_test.go b/go/src/v.io/x/sensorlog/internal/client/measured_v23_test.go
index aba1c73..37572d2 100644
--- a/go/src/v.io/x/sensorlog/internal/client/measured_v23_test.go
+++ b/go/src/v.io/x/sensorlog/internal/client/measured_v23_test.go
@@ -42,7 +42,7 @@
 	time.Sleep(1 * time.Second)
 
 	// Start measured.
-	measuredPath := sh.BuildGoPkg("v.io/x/sensorlog/measured")
+	measuredPath := v23test.BuildGoPkg(sh, "v.io/x/sensorlog/measured")
 	devId := "measured1"
 	publishSb := naming.Join(mtName, measuredSb)
 	measured := sh.Cmd(measuredPath, "-alsologtostderr", "-service="+measuredSb,