Background: as part of the JDK build process, an "exploded build" is created. On Linux, the exploded build can be invoked as ./jdk/bin/java in the build output directory:

    $ ./jdk/bin/java -version
    java version "10-internal"
    Java(TM) SE Runtime Environment (build 10-internal+0-adhoc.iklam.open)
    Java HotSpot(TM) 64-Bit Server VM (build 10-internal+0-adhoc.iklam.open, mixed mode)

The exploded build can be used to to most things that a regular JDK can do. However, it does not have a lib/modules file does not support CDS. When the user attempts to use CDS operations, it fails as expected, but the error message is confusing:

    $ ./jdk/bin/java -Xshare:dump
    Error: non-empty directory '/jdk/bld/cons/jdk/modules/java.base'
    Hint: enable -Xlog:class+path=info to diagnose the failure
    Error occurred during initialization of VM
    CDS allows only empty directories in archived classpaths

It should say something like "CDS is not supported in exploded JDK build".