focal-amd64-hafnium: update to clang 18.1.8

Update clang compiler to 18.1.8.

Change-Id: I842947079f7fc03c78643c731faae291b270f52c
Signed-off-by: Karl Meakin <karl.meakin@arm.com>
diff --git a/focal-amd64-hafnium/Dockerfile b/focal-amd64-hafnium/Dockerfile
index 1f1ffb4..5581fe8 100644
--- a/focal-amd64-hafnium/Dockerfile
+++ b/focal-amd64-hafnium/Dockerfile
@@ -56,9 +56,9 @@
         https://developer.arm.com/-/media/Files/downloads/gnu/11.2-2022.02/binrel/gcc-arm-11.2-2022.02-x86_64-aarch64-none-elf.tar.xz ;\
     tar -Jxf /tmp/gcc-arm-x86_64-aarch64-none-elf.tar.xz -C ${TOOLS_DIR} --strip-components=1 ;\
     # Install LLVM Clang toolchain
-    curl --connect-timeout 5 --retry 8 --retry-delay 2 --create-dirs -fsSLo /tmp/clang+llvm-15.0.6-x86_64-linux-gnu-ubuntu-18.04.tar.xz \
-      https://github.com/llvm/llvm-project/releases/download/llvmorg-15.0.6/clang+llvm-15.0.6-x86_64-linux-gnu-ubuntu-18.04.tar.xz; \
-    tar -xf /tmp/clang+llvm-15.0.6-x86_64-linux-gnu-ubuntu-18.04.tar.xz -C ${TOOLS_DIR} --strip-components=1; \
+    curl --connect-timeout 5 --retry 8 --retry-delay 2 --create-dirs -fsSLo /tmp/clang+llvm-18.1.8-x86_64-linux-gnu-ubuntu-18.04.tar.xz \
+      https://github.com/llvm/llvm-project/releases/download/llvmorg-18.1.8/clang+llvm-18.1.8-x86_64-linux-gnu-ubuntu-18.04.tar.xz; \
+    tar -xf /tmp/clang+llvm-18.1.8-x86_64-linux-gnu-ubuntu-18.04.tar.xz -C ${TOOLS_DIR} --strip-components=1; \
     # Setup environment for sshd
     bash -ex /tmp/tf-environment.install ;\
     # Fix permissions