This patch add the target-* (x86_64-*) as used elsewhere in llvm.
some test never runs due to these features are missing. I realised this when tried to run this one: https://github.com/llvm/llvm-project/blob/master/libunwind/test/remember_state_leak.pass.sh.s#L1
None of these features are used anywhere in the tests as far as I can find. Why add them?
Not used in the tests, I would prefer we don't add features just for the sake of having them.
I think it only makes sense to add those, and the reason is that Lit doesn't allow matching partial triples. We already add the full target triple as a Lit feature, and I think it would be nicer to be able to say something like // REQUIRES: x86_64-linux-* instead of having to add these features. But Lit doesn't do that, so let's add them.