[lldb] [clang] [clang][DebugInfo] Emit global variable definitions for static data members with constant initializers (PR #70639)

[Greg Clayton via cfe-commits]

clayborg wrote:

> Few minor issues, but looks good to me. (you metnioned somewhere an lldb issue I think with this patch when the value is removed from the static member declaration inside the class? If that's a problem - probably hold off on committing this until lldb's been fixed so this doesn't regress things? And document the dependence clearly in the commit message)

I saw the patch to lldb to test that we can find global variables that are `constexpr`. In upstream, we can't use find global variables, but the expression parser does work for these. We should make sure that both `FindGlobalVariables(...)` and expression parsing work for all `constexpr` globals.

https://github.com/llvm/llvm-project/pull/70639