Modified update_llvm.sh to not rely on bashisms
Modified update_llvm.sh to not rely on bashisms

go-llvm/llvm,go-llvm/llvm,axw/go-llvm-testing,axw/go-llvm-testing,go-llvm/llvm,axw/go-llvm-testing,axw/go-llvm-testing,go-llvm/llvm