unit test build failure in phosphor-hwmon

[Brad Bishop]

I was trying to get meson going in phosphor-hwmon today and I stumbled on a  
unit test that doesn’t build under gcc 9.1.0.  The failing test is the  
average test.

I just thought I’d quick throw this out there in case anyone feels like  
having a look.  Also, I think this means our repository CI environment has  
gotten out of sync with upstream Yocto?

I realize “patches welcome” applies here for both issues :-) but I just  
wanted to broadcast them.

thx -brad