cmd/gotext: actually use -dir flag

gotext has the read -dir flag but is not used.
The dir parameter should be passed to pipeline.Config

Fixes golang/go#61507

Change-Id: I242a768964fe56c4c7877de9dc487777c6815dae
Reviewed-on: https://go-review.googlesource.com/c/text/+/512015
Auto-Submit: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Heschi Kreinick <heschi@google.com>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>

cmd/gotext/main.go

@@ -53,6 +53,7 @@ func config() (*pipeline.Config, error) {
 		Supported:           getLangs(),
 		TranslationsPattern: `messages\.(.*)\.json$`,
 		GenFile:             *out,
+		Dir:                 *dir,
 	}, nil
 }