scanner: Fix broken private-code generation

Missing a closing bracket.
Reviewed-by: Daniel Stone <daniels@collabora.com>

src/scanner.c

@@ -1748,7 +1748,7 @@ emit_code(struct protocol *protocol, enum visibility vis)
 		       "# define __has_attribute(x) 0  /* Compatibility with non-clang compilers. */\n"
 		       "#endif\n\n");
 
-		printf("#if (__has_attribute(visibility) || defined(__GNUC__) && __GNUC__ >= 4\n"
+		printf("#if (__has_attribute(visibility) || defined(__GNUC__) && __GNUC__ >= 4)\n"
 		       "#define WL_PRIVATE __attribute__ ((visibility(\"hidden\")))\n"
 		       "#else\n"
 		       "#define WL_PRIVATE\n"