[bug] scrubber fresh install fails to run

The scrubber, part of a fresh download, consistently fails to run with error:
```
The system cannot find the file C:\support-diagnostics-8.1.4\lib\NUL.
Runtimes library does not exist - make sure you are running the archive with 'dist' in the name, not the one labeled: 'source'.
```

Here is more from the scrubber.log:

```
13:12:46.634 [main] INFO com.elastic.support.BaseService - Diagnostic logger reconfigured for inclusion into archive
13:12:46.634 [main] INFO com.elastic.support.scrub.ScrubService - Threadpool configured with 4 workers.
13:12:46.680 [main] ERROR com.elastic.support.scrub.ScrubService - Error occurred:
java.lang.NullPointerException: null
at java.io.Reader.(Reader.java:167) ~[?:?]
at java.io.InputStreamReader.(InputStreamReader.java:113) ~[?:?]
at org.apache.commons.io.IOUtils.copy(IOUtils.java:2440) ~[commons-io-2.6.jar:2.6]
at org.apache.commons.io.IOUtils.toString(IOUtils.java:1084) ~[commons-io-2.6.jar:2.6]
at org.apache.commons.io.IOUtils.toString(IOUtils.java:1110) ~[commons-io-2.6.jar:2.6]
at com.elastic.support.scrub.ScrubService.getNodeInfoFromZip(ScrubService.java:156) ~[support-diagnostics-8.1.4.jar:8.1.4]
at com.elastic.support.scrub.ScrubService.exec(ScrubService.java:54) [support-diagnostics-8.1.4.jar:8.1.4]
at com.elastic.support.scrub.ScrubApp.main(ScrubApp.java:42) [support-diagnostics-8.1.4.jar:8.1.4]
13:12:46.696 [main] ERROR com.elastic.support.scrub.ScrubService - Issue encountered during scrub processing. Check diagnostics.log in the archive file for more detail..
13:12:46.696 [main] INFO com.elastic.support.BaseService - Closing loggers.
13:12:46.696 [main] INFO com.elastic.support.util.SystemUtils - Deleted directory: C:\Software\support-diagnostics-8.1.4\scrubbed-diagnostic-e7bbbc-2021-Jun-29--16_34_35.
```

We definitely downloaded the built package, not the source.
We checked the diagnostic utility, that works fine.
Environment details:
```
Virtual Machine
Java JDK 13.0.2
echo %java_home% C:\Program Files\Java\jdk-13.0.2\
Windows Server 2016
Version 1607
support diagnostic tool 8.1.4
No non default settings
```