Test serviceability/sa/TestJmapCore.java fails with: java.io.IOException: Stack frame 0x4 not found

Following the integration of JDK-8274620, which introduced a buffered output stream, we now see this failure:

----------System.err:(18/998)----------

java.io.IOException: Stack frame 0x4 not found
at jdk.test.lib.hprof.parser.HprofReader.read(HprofReader.java:335)
at jdk.test.lib.hprof.parser.Reader.readFile(Reader.java:95)
at jdk.test.lib.hprof.HprofParser.parse(HprofParser.java:85)
at jdk.test.lib.hprof.HprofParser.parse(HprofParser.java:54)
at TestJmapCore.test(TestJmapCore.java:106)
at TestJmapCore.main(TestJmapCore.java:70)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:76)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:51)
at java.base/java.lang.reflect.Method.invoke(Method.java:569)
at com.sun.javatest.regtest.agent.MainActionHelper$AgentVMRunnable.run(MainActionHelper.java:312)
at java.base/java.lang.Thread.run(Thread.java:833)


Presumably there is a missing flush/close causing the missing output.

Failures on macOs only so far.