[clang] [C++20] [Modules] Don't emit function bodies which is noinline and av… (PR #68501)

[Chuanqi Xu via cfe-commits]

ChuanqiXu9 wrote:

> This doesn't seem all that useful/important to me - a user can move the body of the function into an implementation unit rather than putting it in the interface unit and marking it noinline, right? This is the same recommendation we'd make if someone wrote a complex function definition in a header - and I think it's fine that the advice remains valid/relevant even in a modules build.

It is helpful  for **some** cases. e.g., we're lazy to create the implementation file. (I know it doesn't sound smart but such style exists. And the cost we pay in this patch are really little)

https://github.com/llvm/llvm-project/pull/68501