disable long double on aarch64-darwin

Apple Silicon does not have support for long doubles, so they need to
be disabled.

setup.py

@@ -2,6 +2,7 @@
 # -*- coding: utf-8 -*-
 
 import os
+import platform
 import subprocess
 import sys
 import io
@@ -195,7 +196,7 @@ def _get_have_long_double(self):
         # Ideally this would check the fplll headers explicitly for the
         # the FPLLL_WITH_LONG_DOUBLE define, but for now it suffices to
         # say that long double support is disabled on Cygwin
-        return not sys.platform.startswith("cygwin")
+        return not (sys.platform.startswith("cygwin") or ("macOS" in (_ := platform.platform()) and "arm" in _))
 
 
 # EXTENSIONS