ENH: Update to ubuntu 24.04 and clang-format-19

Dockerfile

@@ -1,12 +1,27 @@
-FROM ubuntu:18.04
+FROM ubuntu:24.04
 
 COPY LICENSE README.md /
 
 RUN apt-get update && apt-get install -y \
-  clang-format-8 \
   git \
   wget \
-  && cd /usr/bin && ln -s clang-format-8 clang-format
+  lsb-release \
+  software-properties-common \
+  gnupg \
+  && apt-get clean
+
+# Download latest .deb packages from llvm.
+# See https://apt.llvm.org/ for instructions.
+RUN wget https://apt.llvm.org/llvm.sh \
+    && chmod +x llvm.sh \
+    && ./llvm.sh 19 \
+    && apt-get install clang-format-19 \
+    && apt-get clean
+
+# The following is a workaround to allow other scripts
+# that were hard-coded to use the unversioned clang-format
+# binary to continue to work.
+RUN cd /usr/bin && rm -rf clang-format && ln -s clang-format-19 clang-format
 
 COPY entrypoint.sh /entrypoint.sh
 RUN chmod +x /entrypoint.sh