BUILD(macos): Fix plugins not getting bundled

If the osxdist script was not executed within the build directory, it
would not bundle the built plugins (most notably the Link plugin) as it
was using a relative path and was ignoring the binary dir command-line
option.

This is remedied by this commit.

Fixes mumble-voip#5571

macx/scripts/osxdist.py

@@ -151,7 +151,7 @@ def copy_plugins(self):
 		dst = os.path.join(self.bundle, 'Contents', 'Plugins')
 		if not os.path.exists(dst):
 			os.makedirs(dst)
-		for plugin in glob.glob('plugins/*.dylib'):
+		for plugin in glob.glob(os.path.join(options.binary_dir, 'plugins') + '/*.dylib'):
 			shutil.copy(plugin, dst)
 
 	def update_plist(self):