Fix and rename build date

- rename from BASE_BUILD_DATE to BASE_CREATED to match label name
- noticed it wasn't a valid utc iso timestamp, so fixed that
- noticed we are using a weird hybrid of make and just, so fixed that

Dockerfile

@@ -34,9 +34,9 @@ EOF
 
 # record build info so downstream images know about the base image they were
 # built from
-ARG BASE_BUILD_DATE
+ARG BASE_CREATED
 ARG BASE_GITREF
-LABEL org.opensafely.base.created=$BASE_BUILD_DATE \
+LABEL org.opensafely.base.created=$BASE_CREATED \
       org.opensafely.base.gitref=$BASE_GITREF
 
 FROM base-docker as base-action

Justfile

@@ -3,14 +3,22 @@ export ACTION_IMAGE_NAME := env_var_or_default('ACTION_IMAGE_NAME', "base-action
 _default:
   @just --list
 
-build:
-  make build
+# build all images
+build *args:
+  #!/bin/bash
+  export DOCKER_BUILDKIT=1
+  export BASE_CREATED=$(date --utc +'%Y-%m-%dT%H:%M:%S+00:00')
+  export BASE_GITREF=$(git rev-parse --short HEAD)
+  docker compose build --pull {{ args }}
+
+clean-build: (build "--no-cache")
 
 # hadolint the Dockerfile
 lint:
   @docker pull hadolint/hadolint
   @docker run --rm -i hadolint/hadolint < Dockerfile
 
+# build and test all images
 test: build
   #!/bin/bash
   set -euxo pipefail

docker-compose.yaml

@@ -9,7 +9,7 @@ services:
         # this makes the image work for later cache_from: usage
         - BUILDKIT_INLINE_CACHE=1
         # env vars supplied by make/just
-        - BASE_BUILD_DATE
+        - BASE_CREATED
         - BASE_GITREF
     init: true