[clang] [Driver] Handle mips*-*-none-elf triples (PR #196322)

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yingopq wrote:

> > We have mips*-mti-elf (for pre-R6), and mips*-img-elf (for r6+) triples. Can these triples meet your requirements?
> 
> This patch is good to me, while the commit msg is quite misleading. In fact you are just mark mips*-elf triples as baremetal not add new triples.

@mojyack It would be best to modify the commit message.

https://github.com/llvm/llvm-project/pull/196322