Yes I can confirm this behaviour.
Look at .inkscape\\makefile.mingw
It is copied to config.h in the make-proccess.
 
HTH,
 
Adib.
-----------------------------------
>
> Can someone verify that the windows build is correctly updating
> "config.h": the g_ascii_strtod macro isn't being defined in the
> autobuilds, it looks like.

AFAIK the windows build uses inkscape/config.h.mingw as its config.h.
Anything that needs to be in config.h must be added here, I think.

Carl