Support ARCHFLAGS

Author: Schwaggot

setup.py

@@ -1,4 +1,5 @@
 import os
+import re
 import sys
 import subprocess
 from pathlib import Path
@@ -28,6 +29,12 @@ def build_extension(self, ext: CMakeExtension) -> None:
 
         build_args = ["--config", "Release"]
 
+        # On macOS, respect ARCHFLAGS for cross-compilation (e.g. x86_64 on arm64)
+        archflags = os.environ.get("ARCHFLAGS", "")
+        archs = re.findall(r"-arch (\S+)", archflags)
+        if archs:
+            cmake_args.append(f"-DCMAKE_OSX_ARCHITECTURES={';'.join(archs)}")
+
         # On Windows, use Ninja if no generator is specified to avoid
         # Visual Studio multi-config generator issues with pybind11
         if sys.platform == "win32" and not cmake_generator: