[llvm] LoongArch: Improve detection of valid TripleABI (PR #147952)

[via llvm-commits]

mintsuki wrote:

> Thanks for the report and patch. Could you please
> 
> * Change the description to include the explanation at [Triples: Environment vs Object format #147665 (comment)](https://github.com/llvm/llvm-project/issues/147665#issuecomment-3051584839) , with potential simplification, so that future contributors reading the commit message do not need to click the link?
> * Add a test to a `clang/test/Driver/loongarch-*.c` file (perhaps loongarch-abi.c) ?

@MaskRay I updated the description, but I am not sure what to change in the `loongarch-abi.c` file. I am new to the LLVM codebase, and therefore I may be missing something, but that test file seems to already test for everything that matters? Like, how would I test for a change that removes a warning?

https://github.com/llvm/llvm-project/pull/147952