Revert "Reapply "[libc++abi] Stop copying headers to the build directory""#115793

arichardson merged 1 commit intomainllvm/llvm-project:mainfrom

revert-115379-users/arichardson/spr/reapply-libcabi-stop-copying-headers-to-the-build-directoryllvm/llvm-project:revert-115379-users/arichardson/spr/reapply-libcabi-stop-copying-headers-to-the-build-directoryCopy head branch name to clipboard