It could be reproduced by specifying the following option with jtreg:
    -vmoptions:-Dtest.dynamic.cds.archive=true

NonExistClasspath.java failed as follows:

----------System.out:(1/43)----------
patchJarForDynamicDump: classpath = foobar
result: Failed. Execution failed: `main' threw exception: java.lang.RuntimeException: FIXME: jar file not at a supported location

ClassPathAttr.java timed out:

result: Error. Program `/scratch/ws/jdk14/build/linux-x64-debug/images/jdk/bin/java' timed out (timeout set to 120000ms, elapsed time including timeout handling was 124182ms).