[clang] [lld] [lld][LoongArch] Add the relaxation option (PR #111488)

[Lu Weining via cfe-commits]

SixWeining wrote:

> How about now?

The patch doesn't touch lld, so my suggestion is "[Driver] Default enable LoongArch linker relaxation".

Some additional comments:
- Do we need to consider the `-gsplit-dwarf` issue #56642 resolved by https://reviews.llvm.org/D130190 ?
- The ``--no-relax`` option should be passed to linker, see #76432
- Pass ``-X`` to linker to discard a plethora of `.L` symbols due to linker relaxation. See https://reviews.llvm.org/D127826


https://github.com/llvm/llvm-project/pull/111488