[libcxx-commits] [libcxx] [libc++] Add missing return 0 to main functions in tests (PR #214190)

[Louis Dionne via libcxx-commits]

ldionne wrote:

> We should really have a CI check for this.

We should test under `-ffreestanding`.  https://github.com/llvm/llvm-project/issues/214385

https://github.com/llvm/llvm-project/pull/214190