[Bug lto/66180] [6 Regression] many -Wodr false positives when building LLVM with -flto

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66180

--- Comment #8 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
If I change foo1.cpp from comment5 to:

#include <memory>
namespace first{
class A {
  int i;
};
}
using namespace first;
class G {
  std::unique_ptr<A> foo() const;
};
std::unique_ptr<A> G::foo() const { return std::make_unique<A>(); }

it works fine. So it looks like a bug after all, because an anonymous namespace
should be equivalent to:

namespace _compiler_generated_name {
...
}
using namespace _compiler_generated_name;