[llvm] [llvm] Use "= default" (NFC) (PR #166088)

[David Spickett via llvm-commits]

DavidSpickett wrote:

I should have been clearer, the error comes from our Flang bots but only because they are the ones enabling LLVM's examples.

My understanding is that you cannot `= default` if you have a member initialiser list as well. Example - https://godbolt.org/z/fj5schPK9

In the CI log I see `LLVM_BUILD_EXAMPLES=ON` but no sign of any files in `llvm/examples being built. Only ones from MLIR and Flang. I suspect that they are not included in `ninja check-llvm`.

https://github.com/llvm/llvm-project/pull/166088