[clang] [Modules] Record whether VarDecl initializers contain side effects (PR #143739)

[Henrik G. Olsson via cfe-commits]

hnrklssn wrote:

> I think this new function should be called from `ASTContext::DeclMustBeEmitted`, no?

Of course, yes! Fixed now.

https://github.com/llvm/llvm-project/pull/143739