cmake: pre-cache HAVE_POLL_FINE on Windows

Windows doesn't support `poll()`, so we can safely skip checking for
fine poll.

Closes #12003

CMake/Platforms/WindowsCache.cmake

@@ -68,6 +68,7 @@ if(NOT UNIX)
     set(HAVE_NET_IF_H 0)
     set(HAVE_IOCTL_SIOCGIFADDR 0)
     set(HAVE_POLL_H 0)
+    set(HAVE_POLL_FINE 0)
     set(HAVE_PWD_H 0)
     set(HAVE_STRINGS_H 0)
     set(HAVE_SYS_FILIO_H 0)