[Devops] Include nightly in main base image (#18725)

Add https://apt.llvm.org/ as an apt repo to get nightly builds.

Author: RossBrunton

devops/containers/ubuntu2404_base.Dockerfile

@@ -4,6 +4,11 @@ ENV DEBIAN_FRONTEND=noninteractive
 
 USER root
 
+# Configure LLVM nightly repo
+RUN apt-get update -qq && apt-get install --no-install-recommends -yqq curl ca-certificates
+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
+
 # Install SYCL prerequisites
 COPY scripts/install_build_tools.sh /install.sh
 RUN /install.sh