We managed the compiler flags our selves
which although allowed, not really needed
CMake has had this option since 3.1.
Also unsure if this is something just
broken in the nightly cmake or this is a
preview of things to come in 3.21/22 but:
When you don't initialize this property it
seems to default to c++14 causing it to pass
both /std:c++17 and /std:c++14 which makes
the MSVC compiler override our C++17 switch
with CMakes C++14 switch leading to build
errors.