[clang] [clang] Emit initializers for static const/constexpr variables once they're met (PR #156933)

[John McCall via cfe-commits]

https://github.com/rjmccall commented:

Initializers can be self-referential, so doing this eagerly might be problematic.

Why does this help with initializing things in consteval functions?

https://github.com/llvm/llvm-project/pull/156933