buildx: bump to version 0.4.2

Signed-off-by: Jérémie Drouet <jeremie.drouet@gmail.com>

Dockerfile

@@ -2,7 +2,7 @@ FROM alpine AS fetcher
 
 RUN apk add curl
 
-ARG BUILDX_VERSION=0.3.1
+ARG BUILDX_VERSION=0.4.2
 RUN curl -L \
   --output /docker-buildx \
   "https://github.com/docker/buildx/releases/download/v${BUILDX_VERSION}/buildx-v${BUILDX_VERSION}.linux-amd64"