[Devops] Add "llvm_nightly" container

This container is based on the base 24.04 container but also configures
https://apt.llvm.org/ as an app repo to get nightly builds.

Author: RossBrunton

.github/workflows/sycl-containers.yaml

@@ -77,6 +77,9 @@ jobs:
               base_image=ghcr.io/intel/llvm/ubuntu2404_build
               base_tag=latest
               use_unstable_driver=false
+          - name: LLVM Nightly Ubuntu 24.04 Docker image
+            file: ubuntu2404_llvm_nightly
+            tag: latest
     steps:
       - name: Checkout
         uses: actions/checkout@v4

devops/containers/ubuntu2404_llvm_nightly.Dockerfile

@@ -0,0 +1,15 @@
+ARG base_tag=latest
+ARG base_image=ghcr.io/intel/llvm/ubuntu2404_base
+
+FROM $base_image:$base_tag
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+USER root
+
+RUN curl -sSL https://apt.llvm.org/llvm-snapshot.gpg.key -o /etc/apt/trusted.gpg.d/apt.llvm.org.asc
+RUN echo 'deb http://apt.llvm.org/noble/ llvm-toolchain-noble main' > /etc/apt/sources.list.d/llvm.list
+
+USER sycl
+
+ENTRYPOINT ["/docker_entrypoint.sh"]