build(macos): add configurable target architecture for DMG builds

CONTRIBUTING.md

@@ -118,3 +118,10 @@ To build the standalone application for your current OS:
 make build
 ```
 This will trigger the Python backend build via PyInstaller.
+
+On macOS, you can choose the target architecture for the DMG build with `NEGPY_MACOS_ARCH`.
+For an Intel build from a compatible macOS environment, run:
+
+```bash
+NEGPY_MACOS_ARCH=x86_64 make build
+```

README.md

@@ -89,6 +89,8 @@ Since this is a free hobby project, I don't pay Apple or Microsoft ransom for th
 2.  Open Terminal and run: `xattr -cr /Applications/NegPy.app` (this gets rid of the warning).
 3.  Launch it.
 
+If you build the DMG yourself on macOS, set `NEGPY_MACOS_ARCH=x86_64` for an Intel build or `NEGPY_MACOS_ARCH=arm64` for Apple Silicon.
+
 **Scanner support** requires SANE via [Homebrew](https://brew.sh/):
 ```
 brew install sane-backends

build.py

@@ -24,6 +24,11 @@
 is_macos = system == "Darwin"
 is_linux = system == "Linux"
 
+
+def get_macos_target_arch():
+    """Return the macOS target architecture for packaging."""
+    return os.environ.get("NEGPY_MACOS_ARCH", platform.machine())
+
 # Basic PyInstaller arguments
 params = [
     ENTRY_POINT,
@@ -119,6 +124,9 @@ def collect_gphoto2_plugins() -> None:
     elif os.path.exists("media/icons/icon.png"):
         params.append("--icon=media/icons/icon.png")
 
+    macos_target_arch = get_macos_target_arch()
+    params.append(f"--target-arch={macos_target_arch}")
+
 
 def package_linux():
     """Package the built application into an AppImage."""
@@ -305,7 +313,7 @@ def package_macos():
     """Package the built application into a DMG with Applications symlink."""
     print(f"Packaging for macOS (DMG) version {VERSION}...")
     app_path = os.path.join("dist", f"{APP_NAME}.app")
-    dmg_name = f"{APP_NAME}-{VERSION}-macOS-{platform.machine()}.dmg"
+    dmg_name = f"{APP_NAME}-{VERSION}-macOS-{get_macos_target_arch()}.dmg"
     dmg_path = os.path.join("dist", dmg_name)
     temp_dmg_dir = os.path.join("dist", "dmg_temp")