vintner: skip VsDevCmd's telemetry upload.

There's no telemetry endpoint reachable (or wanted) under Wine. Rather than
touching the conditional logic below, just set the opt-out switch the
script already checks for on its own.

diff --git a/Common7/Tools/VsDevCmd.bat b/Common7/Tools/VsDevCmd.bat
index f925e95..f3710ad 100644
--- a/Common7/Tools/VsDevCmd.bat
+++ b/Common7/Tools/VsDevCmd.bat
@@ -247,6 +247,7 @@ exit /B 0
 :end
 
 @REM Send Telemetry if user's VS is opted-in
+set "VSCMD_SKIP_SENDTELEMETRY=1"
 if "%VSCMD_SKIP_SENDTELEMETRY%"=="" (
     if "%VSCMD_DEBUG%" NEQ "" (
         @echo [DEBUG:%~nx0] Sending telemetry