Remove v prefix when pkgmacos is called

Existing Mac OS release artifacts use the tag name / version in the file name but drop the `v` prefix.  This does the same for the Mac OS installer.

script/pkgmacos

@@ -30,7 +30,7 @@ while [ $# -gt 0 ]; do
     exit 1
     ;;
   * )
-    tag_name="$1"
+    tag_name="${1#v}"
     shift 1
     ;;
   esac