ZipFiles.zipDirectory leaks native JVM memory

Noticed this in a long-running JVM process starting multiple Dataflow pipelines. Heap usage slowly rose as observed by jcmd <pid> VM.native_memory summary.diff, but a heap dump did not show a consistent amount of usage.

Followed this guide for identify native memory leaks, which pointed me to java.util.ZipFile.

We use it in runners.core-construction.PipelineResources via sdk.util.ZipFiles

Closing the ZipOutputStream here seems to alleviate the issue.