[clang] [clang][LoongArch] Pick the default ABI of environment-less triples from the architecture (PR #231441)

[via cfe-commits]

Mintsuki wrote:

This leaves one case open, on which I would like the maintainers' opinion: a triple whose
environment implies a hard-float ABI, such as loongarch32-unknown-linux-gnu, still gets ilp32d
together with the default 32-bit architecture, which has no FPU, and so still warns and has the
same disagreement. Should the default architecture for such an environment provide the FPU its
ABI needs (adding +f and +d, as for the 64-bit defaults), or should these triples default to
another ABI? I left them unchanged here, as the right answer depends on what LoongArch32 Linux
systems are expected to look like.

@SixWeining @heiher


https://github.com/llvm/llvm-project/pull/231441