Unknown command v - for a list of valid commands use /help.

[John Neffenger]

> $ grep -A2 'reg query' build/vcvarsall.log
> C:\cygwin64\home\john\src\jfx>for /F "tokens=1,2*" %i in
> ('reg query "HKLM\SOFTWARE\Wow6432Node\Microsoft\Microsoft SDKs\Windows\v10.0"

I did it again -- started a line with a Windows command option inside a 
Shell Session code block, resulting in a truncated message on the 
mailing list and the feedback:

   Unknown command v - for a list of valid commands use /help.

For my full comment, please see:

https://github.com/openjdk/jfx/pull/488#issuecomment-848264495

Sorry about that.

John