[libc][nfc] Use common implementation of read_first_lane_u64#131027

JonChesterfield merged 1 commit intollvm:mainllvm/llvm-project:mainfrom

JonChesterfield:jc_common_read_first_lane_u64JonChesterfield/llvm-project:jc_common_read_first_lane_u64Copy head branch name to clipboard