windows: don't attempt to copy libffi DLL during static builds

Without this, the build fails. This may have regressed as part of
upgrading Python 3.8. But I'm unsure why, as I don't see an obvious
diff in the CPython source code that would trigger it.

Author: indygreg

cpython-windows/build.py

@@ -672,6 +672,12 @@ def copy_link_to_lib(p: pathlib.Path):
   </Target>
 """
 
+LIBFFI_PROPS_REMOVE_RULES = b"""
+  <Target Name="_CopyLIBFFIDLL" Inputs="@(_LIBFFIDLL)" Outputs="@(_LIBFFIDLL->'$(OutDir)%(Filename)%(Extension)')" AfterTargets="Build">
+    <Copy SourceFiles="@(_LIBFFIDLL)" DestinationFolder="$(OutDir)" />
+  </Target>
+"""
+
 
 def hack_props(
     td: pathlib.Path,
@@ -793,6 +799,10 @@ def hack_props(
             b"<AdditionalDependencies>libffi.lib;%(AdditionalDependencies)</AdditionalDependencies>",
         )
 
+        static_replace_in_file(
+            libffi_props, LIBFFI_PROPS_REMOVE_RULES.strip().replace(b"\n", b"\r\n"), b""
+        )
+
 
 def hack_project_files(
     td: pathlib.Path,