Rename `.buildx` Dockerfiles to `.buildkit`

This is a more accurate name, since these Dockerfiles require BuildKit, not Buildx.

.github/workflows/release.yml

@@ -48,7 +48,10 @@ jobs:
         ports:
           - 5000:5000
     env:
-      DOCKER_BUILDKIT: 1 # Disabled for now, but we should look at this because it will speedup building!
+      # Use BuildKit (https://docs.docker.com/build/buildkit/) for better
+      # build performance and the ability to copy extended file attributes
+      # (e.g., for executable capabilities) across build phases.
+      DOCKER_BUILDKIT: 1
       # DOCKER_REPO/secrets.DOCKERHUB_REPO needs to be 'index.docker.io/<user>/<repo>'
       DOCKER_REPO: ${{ secrets.DOCKERHUB_REPO }}
       SOURCE_COMMIT: ${{ github.sha }}

docker/Dockerfile.j2

@@ -50,7 +50,7 @@
 {% else %}
 {%   set package_arch_target_param = "" %}
 {% endif %}
-{% if "buildx" in target_file %}
+{% if "buildkit" in target_file %}
 {%   set mount_rust_cache = "--mount=type=cache,target=/root/.cargo/git --mount=type=cache,target=/root/.cargo/registry " %}
 {% else %}
 {%   set mount_rust_cache = "" %}

docker/Makefile

@@ -8,8 +8,8 @@ all: $(OBJECTS)
 %/Dockerfile.alpine: Dockerfile.j2 render_template
 	./render_template "$<" "{\"target_file\":\"$@\"}" > "$@"
 
-%/Dockerfile.buildx: Dockerfile.j2 render_template
+%/Dockerfile.buildkit: Dockerfile.j2 render_template
 	./render_template "$<" "{\"target_file\":\"$@\"}" > "$@"
 
-%/Dockerfile.buildx.alpine: Dockerfile.j2 render_template
+%/Dockerfile.buildkit.alpine: Dockerfile.j2 render_template
 	./render_template "$<" "{\"target_file\":\"$@\"}" > "$@"

hooks/build

@@ -34,9 +34,9 @@ for label in "${LABELS[@]}"; do
     LABEL_ARGS+=(--label "${label}")
 done
 
-# Check if DOCKER_BUILDKIT is set, if so, use the Dockerfile.buildx as template
+# Check if DOCKER_BUILDKIT is set, if so, use the Dockerfile.buildkit as template
 if [[ -n "${DOCKER_BUILDKIT}" ]]; then
-    buildx_suffix=.buildx
+    buildkit_suffix=.buildkit
 fi
 
 set -ex
@@ -45,6 +45,6 @@ for arch in "${arches[@]}"; do
     docker build \
            "${LABEL_ARGS[@]}" \
            -t "${DOCKER_REPO}:${DOCKER_TAG}-${arch}" \
-           -f docker/${arch}/Dockerfile${buildx_suffix}${distro_suffix} \
+           -f docker/${arch}/Dockerfile${buildkit_suffix}${distro_suffix} \
            .
 done