Allow non-void static setter methods when compiling with -opt

[kennykerr]

Fixes #1062

[oldnewthing]

Similar problem exists with void methods.

namespace MyProject
{
    static runtimeclass Sample
    {
        static void M1();
    }
}

namespace winrt::MyProject::implementation
{
    struct Sample
    {
        Sample() = default;

        static int M1() { return 1; }
    };
}

Code gen:

WINRT_EXPORT namespace winrt::MyProject
{
    void Sample::M1()
    {
        return MyProject::implementation::Sample::M1(); // error: returning value from non-void function
    }
}

[kennykerr]

@oldnewthing good catch - updated.