I believe JDK-8326412 caused a regression:

% make test TEST=tools/jlink/CheckExecutable.java

STDERR:
java.lang.RuntimeException: /local/home/shipilev/shipilev-jdk/build/linux-x86_64-server-fastdebug/images/jdk/bin/jstat.debuginfo is not executable!
        at CheckExecutable.main(CheckExecutable.java:62)
        at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103)
        at java.base/java.lang.reflect.Method.invoke(Method.java:580)
        at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:333)
        at java.base/java.lang.Thread.run(Thread.java:1575)

JavaTest Message: Test threw exception: java.lang.RuntimeException
JavaTest Message: shutting down test