Just do "make jdk.jshell":

brian:jdk9$ build/linux-x86-normal-server-release/jdk/bin/jshell
Exception in thread "main" java.lang.UnsatisfiedLinkError: no prefs in java.library.path
        at java.lang.ClassLoader.loadLibrary(ClassLoader.java:1862)
        at java.lang.Runtime.loadLibrary0(Runtime.java:874)
        at java.lang.System.loadLibrary(System.java:1770)

[2/22/16, 11:58:19 AM] Brian Goetz: and if I then do "make java.prefs", I get:

brian:jdk9$ build/linux-x86-normal-server-release/jdk/bin/jshell
java.util.ServiceConfigurationError: com.sun.jdi.connect.Connector: Provider sun.jvm.hotspot.jdi.SACoreAttachingConnector not found
java.util.ServiceConfigurationError: com.sun.jdi.connect.Connector: Provider sun.jvm.hotspot.jdi.SADebugServerAttachingConnector not found
java.util.ServiceConfigurationError: com.sun.jdi.connect.Connector: Provider sun.jvm.hotspot.jdi.SAPIDAttachingConnector not found
Exception in thread "main" java.lang.InternalError: Failed remote launch: com.sun.jdi.CommandLineLaunch (defaults: home=/home2/brian/jdk9/build/linux-x86-normal