libffi: Always define `WIN32_LEAN_AND_MEAN` before <windows.h>

From commit:
902c755930326cb4405672aa3ea13c35c653cbff - Always define `WIN32_LEAN_AND_MEAN` before <windows.h>

Forwarded upstream: https://github.com/libffi/libffi/pull/937

libffi/ChangeLog:
	PR libffi/117635
	* src/aarch64/ffi.c: Define `WIN32_LEAN_AND_MEAN` before
	`#include <windows.h>`.

Signed-off-by: Pietro Monteiro <pietro@sociotechnical.xyz>