hg: jdk/jdk: 8240231: Build failure on illumos after 8238988

[daniel.daugherty at oracle.com]

Changeset: 1a57db1b936f
Author:    dcubed
Date:      2020-02-28 10:16 -0500
URL:       https://hg.openjdk.java.net/jdk/jdk/rev/1a57db1b936f

8240231: Build failure on illumos after 8238988
Summary: add missing cast
Reviewed-by: dcubed, shade
Contributed-by: peter.tribble at gmail.com

! src/hotspot/os_cpu/solaris_x86/thread_solaris_x86.cpp