Build multi-arch container images across stack
diff --git a/apps/bwolf-gandi/Dockerfile b/apps/bwolf-gandi/Dockerfile
index 6fee6aa..df46fc1 100644
--- a/apps/bwolf-gandi/Dockerfile
+++ b/apps/bwolf-gandi/Dockerfile
@@ -1,8 +1,10 @@
 FROM alpine:3.9
 
+ARG TARGETARCH
+
 RUN apk add --no-cache ca-certificates
 
-COPY webhook /usr/local/bin/webhook
+COPY webhook_${TARGETARCH} /usr/local/bin/webhook
 RUN chmod +x /usr/local/bin/webhook
 
 ENTRYPOINT ["webhook"]