functional tests don't compile on jdknext

[pshipton]

https://ci.eclipse.org/openj9/job/Test_openjdknext_j9_extended.functional_s390x_linux_OpenJDK/64
https://ci.eclipse.org/openj9/job/Test_openjdknext_j9_sanity.functional_s390x_linux_OpenJDK/77
https://ci.eclipse.org/openj9/job/Test_openjdknext_j9_sanity.functional_x86-64_windows_OpenJDK/63
etc. for all platforms.

06:49:30  compile:
06:49:30       [echo] Ant version is Apache Ant(TM) version 1.9.6 compiled on July 20 2018
06:49:30       [echo] ============COMPILER SETTINGS============
06:49:30       [echo] ===fork:                         yes
06:49:30       [echo] ===executable:                   /home/jenkins/jenkins-agent/workspace/Test_openjdknext_j9_extended.functional_s390x_linux_OpenJDK/openjdkbinary/j2sdk-image/bin/javac
06:49:30       [echo] ===debug:                        on
06:49:30       [echo] ===destdir:                      /home/jenkins/jenkins-agent/workspace/Test_openjdknext_j9_extended.functional_s390x_linux_OpenJDK/openjdk-tests/functional/cmdLineTests/jvmtitests/bin
06:49:30      [javac] Compiling 317 source files to /home/jenkins/jenkins-agent/workspace/Test_openjdknext_j9_extended.functional_s390x_linux_OpenJDK/openjdk-tests/functional/cmdLineTests/jvmtitests/bin
06:49:31      [javac] /home/jenkins/jenkins-agent/workspace/Test_openjdknext_j9_extended.functional_s390x_linux_OpenJDK/openjdk-tests/functional/cmdLineTests/jvmtitests/src/com/ibm/jvmti/tests/util/SyncThread.java:63: error: invalid use of a restricted identifier 'yield'
06:49:31      [javac]         	yield();
06:49:31      [javac]         	^
06:49:31      [javac]   (to invoke a method called yield, qualify the yield with a receiver or type name)
06:49:31      [javac] /home/jenkins/jenkins-agent/workspace/Test_openjdknext_j9_extended.functional_s390x_linux_OpenJDK/openjdk-tests/functional/cmdLineTests/jvmtitests/src/com/ibm/jvmti/tests/util/SyncThread.java:69: error: invalid use of a restricted identifier 'yield'
06:49:31      [javac]         yield();
06:49:31      [javac]         ^
06:49:31      [javac]   (to invoke a method called yield, qualify the yield with a receiver or type name)
06:49:31      [javac] 2 errors

[pshipton]

previous working build:
OpenJ9: 64087aa
OMR: b372b24
OpenJDKnext: 3657615 - openj9-openjdk-jdk

failing build:
OpenJ9: 881cb8e
OMR: b372b24
OpenJDKnext: 83ad409 - openj9-openjdk-jdk

64087aa...881cb8e

The test didn't change, I believe the problem is that javac changed.