I found I had to build Richard Burton's esptool2 from the supplied source (C:\Espressif\examples\ESP8266\rboot\esptool2\) . It built first try in Visual Studio, then I moved the exe to somewhere in my path (C:\Espressif\utils).
So anyway, I've got some of the SmingRTOS examples bulding and working, and I'm now trying to convert one of my old projects to SmingRTOS.
More news when I have some.