RFR: JDK-8266396: Add VSCMD_DEBUG for solving WINSDK_DIR build error

[John Neffenger]

On 5/6/21 1:46 PM, John Neffenger wrote:
> $ reg query "HKLM\SOFTWARE\Microsoft\VisualStudio\VSPerf" \

The last part of my comment was truncated by Skara when it tripped over 
the '/v' Windows command-line option. It's repeated below for the 
mailing list ...

We could instead set the default value to "3". In that case, I get two 
error messages during the Windows build due to following registry query 
failing on my system:

$ reg query "HKLM\SOFTWARE\Microsoft\VisualStudio\VSPerf" /v 
"CollectionToolsDir2019"
ERROR: The system was unable to find the specified registry key or value.

### Wiki

I suggest that we remove the "Missing paths issue" section from the 
Wiki, added on October 31, 2019. It only led me astray. If you get 
`WINSDK_DIR not defined`, it's an error, and you should find its source 
and fix it. This pull request can help.