Bump default version in buid script

Author: Ewa Matejska

utils/build-script

@@ -2072,7 +2072,7 @@ iterations with -O",
         "--swift-user-visible-version",
         help="User-visible version of the embedded Swift compiler",
         type=arguments.type.swift_compiler_version,
-        default="4.0",
+        default="4.1",
         metavar="MAJOR.MINOR")
 
     parser.add_argument(