Add --load flag for docker buildx

Without there was a warning: No output specified with docker-container driver. Build result will only remain in the build cache.

justfile

@@ -47,14 +47,14 @@ build base_version="" tag=default_tag:
     #!/usr/bin/env bash
     set -euxo pipefail
     [[ "{{base_version}}" == "" ]] && build_arg="" || build_arg="--build-arg BASE_IMAGE_VERSION={{base_version}}"
-    docker buildx build {{ platform_arg }} $build_arg -t {{ image }}:{{tag}}  .
+    docker buildx build --load {{ platform_arg }} $build_arg -t {{ image }}:{{tag}}  .
 
 # Shortcut to build the R2DT Docker image against custom base image
 tag-build tag: (build tag tag)
 
 # Build base image locally
 bbuild:
-    docker buildx build {{ platform_arg }} -t {{ base_image }} base_image
+    docker buildx build --load {{ platform_arg }} -t {{ base_image }} base_image
 
 # Build base and then the r2dt images locally
 full-build: bbuild (tag-build "latest")