valhalla doesn't build :(

[Remi Forax]

It seems that trying t obuild the valhalla repo doesn't work by default :(

* For target jdk_modules_java.base__the.java.base_batch:
/home/forax/java/workspace/mvt/valhalla/jdk/src/java.base/share/classes/java/lang/__Value.java:31: error: value classes allowed only with -XDenableValueTypes option to the compiler
__ByValue final public class __Value {
^
1 error

cheers,
Rémi