[lld] [lld] Add target support for SystemZ (s390x) (PR #75643)

[Nathan Chancellor via llvm-commits]

nathanchance wrote:

I have sent https://lore.kernel.org/20240207-s390-lld-and-orphan-warn-v1-0-8a665b3346ab@kernel.org/ for the Linux kernel, which passes my build tests with both Clang and GCC for `defconfig` and `allmodconfig` (minus `CONFIG_BUG`, which I bring up in the cover letter).

https://github.com/llvm/llvm-project/pull/75643