Disable the use of ninja for windows builds

Aperantly github added ninja to all of there runners now. This
causes the windows build to fail. This is expected because we
add the architecture as a compiler arg which is not known to
ninja. Even with this the build fails.

This commit disables ninja on windows for now. Once we fixed the
underlying issue with ninja and windows we can reenable it.

buildutils/build.py

@@ -28,7 +28,7 @@ def build_libcapnp(bundle_dir, build_dir):  # noqa: C901
 
     # Enable ninja for compilation if available
     build_type = []
-    if shutil.which("ninja"):
+    if shutil.which("ninja") and os.name != "nt":
         build_type = ["-G", "Ninja"]
 
     # Determine python shell architecture for Windows