LOC-7291: download darwin-arm64 binary on Apple Silicon

On macOS the binding now selects BrowserStackLocal-darwin-arm64 when
the runtime reports arm64 (same runtime-arch detection the linux-arm64
path already uses); x64 runtimes (including x64-under-Rosetta) keep
BrowserStackLocal-darwin-x64, preserving current behavior.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: vivianludrick

lib/LocalBinary.js

@@ -93,7 +93,11 @@ function LocalBinary(){
 
   this.getBinaryFilename = function() {
     if(this.hostOS.match(/darwin|mac os/i)){
-      return 'BrowserStackLocal-darwin-x64';
+      if(this.isArm64) {
+        return 'BrowserStackLocal-darwin-arm64';
+      } else {
+        return 'BrowserStackLocal-darwin-x64';
+      }
     } else if(this.hostOS.match(/mswin|msys|mingw|cygwin|bccwin|wince|emc|win32/i)) {
       this.windows = true;
       return 'BrowserStackLocal.exe';

test/local.js

@@ -393,10 +393,19 @@ describe('LocalBinary', function () {
     it('should return darwin binary filename', function() {
       ['darwin', 'mac os'].forEach(function(os) {
         localBinary.hostOS = os;
+        localBinary.isArm64 = false;
         expect(localBinary.getBinaryFilename()).to.equal('BrowserStackLocal-darwin-x64');
       });
     });
 
+    it('should return darwin arm64 binary filename', function() {
+      ['darwin', 'mac os'].forEach(function(os) {
+        localBinary.hostOS = os;
+        localBinary.isArm64 = true;
+        expect(localBinary.getBinaryFilename()).to.equal('BrowserStackLocal-darwin-arm64');
+      });
+    });
+
     it('should return exe binary filename', function() {
       ['mswin', 'msys', 'mingw', 'cygwin', 'bccwin', 'wince', 'emc', 'win32'].forEach(function(os) {
         localBinary.hostOS = os;