Fix architecture detection for macOS Intel CPUs

Looks like this was never tested on real x86 macOS hardware. Testing it now for the desktop release and the detection doesn't work like this.

bramble-java/src/main/java/org/briarproject/bramble/plugin/tor/MacTorPluginFactory.java

@@ -66,7 +66,7 @@ public class MacTorPluginFactory extends TorPluginFactory {
 		if (LOG.isLoggable(INFO)) {
 			LOG.info("System's os.arch is " + arch);
 		}
-		if (arch.equals("amd64")) return "x86_64";
+		if (arch.equals("x86_64")) return "x86_64";
 		else if (arch.equals("aarch64")) return "aarch64";
 		return null;
 	}