lock base container to use ubuntu 24.

Author: RossBugginsNHS

src/devcontainers/base/Makefile

@@ -2,7 +2,8 @@ CONTAINER_PREFIX=ghcr.io/nhsdigital/nhs-notify-devcontainer-
 CONTAINER_NAME=base
 BASE_CONTAINER_PREFIX=mcr.microsoft.com/devcontainers/
 BASE_CONTAINER_NAME=base
-BASE_IMAGE_TAG=ubuntu-24.04
+BASE_IMAGE_TAG=""
+BASE_IMAGE_TAG_LOCKED=ubuntu-24.04
 IMAGE_NAME=${CONTAINER_PREFIX}$(CONTAINER_NAME)
 WORKSPACE_FOLDER=.
 
@@ -11,7 +12,7 @@ build:
 	BUILDKIT_PROGRESS=plain \
 	BASE_CONTAINER_NAME=$(BASE_CONTAINER_NAME) \
 	CONTAINER_NAME=$(CONTAINER_NAME) \
-	BASE_IMAGE_TAG=$(BASE_IMAGE_TAG) \
+	BASE_IMAGE_TAG=$(BASE_IMAGE_TAG_LOCKED) \
 	BASE_CONTAINER_PREFIX=$(BASE_CONTAINER_PREFIX) \
 	devcontainer build \
 	--push false \
@@ -24,7 +25,7 @@ build_no_cache:
 	BUILDKIT_PROGRESS=plain \
 	BASE_CONTAINER_NAME=$(BASE_CONTAINER_NAME) \
 	CONTAINER_NAME=$(CONTAINER_NAME) \
-	BASE_IMAGE_TAG=$(BASE_IMAGE_TAG) \
+	BASE_IMAGE_TAG=$(BASE_IMAGE_TAG_LOCKED) \
 	BASE_CONTAINER_PREFIX=$(BASE_CONTAINER_PREFIX) \
 	devcontainer build \
 	--push false \