In the review for JDK-8235907 it has been found that the above directory has been added by mistake, and actually is not part of upstream Graal any more and should be removed.
See https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2019-December/028163.html for this.
See https://mail.openjdk.java.net/pipermail/hotspot-gc-dev/2019-December/028163.html for this.