[llvm] [CMake] Check objcopy support for LLVM_SPLIT_DWARF (PR #80500)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

@MaskRay : on top of what @jsji wrote, don't you think that this check is "low-cost" while providing a safeguard to our users for a behavior that would be hard to figure out for them? (and for whoever has to provide support for when such user will ask for help on Discourse...)?

I mean we require a minimum version of the toolchain and we check for it, so why not do the same for other tools?

https://github.com/llvm/llvm-project/pull/80500