Replace COPY with bind mount in modules examples

.test/tests/modules/run.sh

@@ -32,7 +32,7 @@ fi
 
 # Create an instance of the container-under-test
 modulesImage="$("$HOME/oi/test/tests/image-name.sh" librarytest/nginx-template "$image")"
-DOCKER_BUILDKIT=0 docker build --build-arg NGINX_FROM_IMAGE="$image" --build-arg ENABLED_MODULES="ndk set-misc echo" -t "$modulesImage" -f "modules/$dockerfile" "$GITHUB_WORKSPACE/modules"
+docker build --build-arg NGINX_FROM_IMAGE="$image" --build-arg ENABLED_MODULES="ndk set-misc echo" -t "$modulesImage" -f "modules/$dockerfile" "$GITHUB_WORKSPACE/modules"
 
 serverImage="${modulesImage}-sme"
 "$HOME/oi/test/tests/docker-build.sh" "$dir" "$serverImage" <<EOD

modules/Dockerfile

@@ -70,12 +70,11 @@ RUN set -ex \
     && echo "BUILT_MODULES=\"$BUILT_MODULES\"" > /tmp/packages/modules.env
 
 FROM ${NGINX_FROM_IMAGE}
-COPY --from=builder /tmp/packages /tmp/packages
-RUN set -ex \
+RUN --mount=type=bind,target=/tmp/packages/,source=/tmp/packages/,from=builder \
+    set -ex \
     && apt update \
     && . /tmp/packages/modules.env \
     && for module in $BUILT_MODULES; do \
            apt install --no-install-suggests --no-install-recommends -y /tmp/packages/nginx-module-${module}_${NGINX_VERSION}*.deb; \
        done \
-    && rm -rf /tmp/packages \
     && rm -rf /var/lib/apt/lists/

modules/Dockerfile.alpine

@@ -62,10 +62,9 @@ RUN set -ex \
     && echo "BUILT_MODULES=\"$BUILT_MODULES\"" > /tmp/packages/modules.env
 
 FROM ${NGINX_FROM_IMAGE}
-COPY --from=builder /tmp/packages /tmp/packages
-RUN set -ex \
+RUN --mount=type=bind,target=/tmp/packages/,source=/tmp/packages/,from=builder \
+    set -ex \
     && . /tmp/packages/modules.env \
     && for module in $BUILT_MODULES; do \
            apk add --no-cache --allow-untrusted /tmp/packages/nginx-module-${module}-${NGINX_VERSION}*.apk; \
-       done \
-    && rm -rf /tmp/packages
+       done

modules/README.md

@@ -5,6 +5,17 @@ your own instuctions following a simple filesystem layout/syntax using
 `build_module.sh` helper script, or falling back to package sources from
 [pkg-oss](https://hg.nginx.org/pkg-oss).
 
+## Requirements
+
+To use the Dockerfiles provided here,
+[Docker BuildKit](https://docs.docker.com/build/buildkit/) is required.
+This is enabled by default as of version 23.0; for earlier versions this can be
+enabled by setting the environment variable `DOCKER_BUILDKIT` to `1`.
+
+If you can not or do not want to use BuildKit, you can use a previous version
+of these files, see for example
+https://github.com/nginxinc/docker-nginx/tree/4bf0763f4977fff7e9648add59e0540088f3ca9f/modules.
+
 ## Usage
 
 ```