Update LLVM from 18 to 21 In Ubuntu 24

Here’s I do it, first install the llvm 21: wget https://apt.llvm.org/llvm.sh chmod +x llvm.sh sudo ./llvm.sh 21 Then install all LLVM tools sudo apt install llvm-21* clang-21* lld-21* lldb-21* Then install the alternatives (see the script) wget htt...