Dockerfile: add ALPINE_VERSION build-arg

This allows us to pin to a specific version of Alpine, in case the
golang:alpine image switches to a newer version, which may at times
be incompatible, e.g. see https://github.com/moby/moby/issues/44570

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

dockerfiles/Dockerfile.dev

@@ -1,11 +1,12 @@
 # syntax=docker/dockerfile:1
 
 ARG GO_VERSION=1.19.3
+ARG ALPINE_VERSION=3.16
 
 ARG BUILDX_VERSION=0.9.0
 FROM docker/buildx-bin:${BUILDX_VERSION} AS buildx
 
-FROM golang:${GO_VERSION}-alpine AS golang
+FROM golang:${GO_VERSION}-alpine${ALPINE_VERSION} AS golang
 ENV  CGO_ENABLED=0
 
 FROM golang AS gofumpt