Revert "Synapse : construire image sans buildkit #15"

This reverts commit d10cb82e24.

podman-matrix/ci_build-images.sh

@@ -12,7 +12,16 @@ buildfolder=/tmp/synapse-$$
 if ! podman image exists ${synapse_image}:${synapse_version}; then
     mkdir ${buildfolder} &&
     curl -sSfL -- "https://github.com/matrix-org/synapse/archive/refs/tags/${synapse_version}.tar.gz" | \tar xz --strip-components 1 -C ${buildfolder}/ && {
-        podman build -t ${synapse_image}:${synapse_version} -f ${buildfolder}/docker/Dockerfile ${buildfolder}/
+        podman image pull docker.io/moby/buildkit:latest
+        podman container run -d --name buildkitd --privileged docker.io/moby/buildkit:latest &&
+        my_buildctl --addr=podman-container://buildkitd build \
+		       --frontend dockerfile.v0 \
+		       --local context=${buildfolder}/ \
+		       --local dockerfile=${buildfolder}/docker/ \
+		       --output type=oci,name="${synapse_image}:${synapse_version}" | \
+                       podman image load &&
+	podman container rm --force buildkitd &&
+	podman image rm docker.io/moby/buildkit:latest
     }
     rm -rf ${buildfolder}
 else