Disable warnings about generated spectre mitigations
Disable warnings about generated spectre mitigations

On newer versions of MSVC, the compiler warns at `/Wall` if it will
generate a FENCE to mitigate against spectre

https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/c5045?view=vs-2019

This breaks testing, and is uninteresting for our purposes.

sheredom/utest.h,sheredom/utest.h