Update to clang 18 prebuilt

Author: gsingh93

Makefile

@@ -8,7 +8,7 @@ SCRIPT_DIR := $(ROOT_DIR)/scripts
 CONFIG_DIR := $(ROOT_DIR)/config
 CLANG_DIR ?= $(ROOT_DIR)/toolchain/clang
 
-CLANG_URL := 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
+CLANG_URL := https://mirrors.edge.kernel.org/pub/tools/llvm/files/llvm-18.1.3-x86_64.tar.xz
 
 SHARED_DIR := $(ROOT_DIR)/shared