[llvm] [llvm] [Triple] Add QNX Neutrino RTOS to llvm::Triple (PR #97417)

[Pavel Labath via llvm-commits]

labath wrote:

Since you are going to be changing LLVM code as well, and also imposing a requirement that llvm (at least the parts of it used by lldb) need to work on the new operating system, I think the RFC should go the llvm list. You don't need to focus on the lldb specifics (we can deal with that in separate RFC if needed). Instead, I think the focus should be on what llvm changes are needed (I see you're adding a new Triple entry, but is that the only thing?), and why (so that lldb can detect that its debugging a process on this system?).

Explaining how you are able to get debugger support without toolchain support (as lldb basically embeds llvm&clang) would also be helpful. Is it the case that this operating system is sufficiently similar to existing systems, that the compiler can generate code for it by treating it as a generic `$arch-unkown-elf` system, but that lldb (since it needs to interact with the system more) needs to special-case it.

https://github.com/llvm/llvm-project/pull/97417