[clang] [libc++] Fix the behavior of throwing `operator new` under -fno-exceptions (PR #69498)

[via cfe-commits]

EricWF wrote:

> We currently support both ways of building the library (-fexceptions and -fno-exceptions). I don't know how widely used the -fno-exceptions variant is used and we could discuss dropping it (and forcing people to always build the library itself with -fexceptions), but IMO this should be a separate change. In practice, I suspect that a lot of folks in the embedded world might be building the library with -fno-exceptions.

My only concern is that this change introduces a bunch of black-magic, which I suspect is pretty fragile (but I don't know), and I would like to avoid that if possible.



https://github.com/llvm/llvm-project/pull/69498