Fix WSL Check to work if we dont know if we are running under linux yet

vscode-dotnet-runtime-library/src/Utils/CommandExecutor.ts

@@ -77,10 +77,20 @@ export class CommandExecutor extends ICommandExecutor
     {
         // See https://github.com/microsoft/WSL/issues/4071 for evidence that we can rely on this behavior.
 
+        if(os.platform() !== 'linux')
+        {
+            return false;
+        }
+
         const command = 'grep';
         const args = ['-i', 'Microsoft', '/proc/version'];
         const commandResult = proc.spawnSync(command, args);
 
+        if(!commandResult || !commandResult.stdout)
+        {
+            return false;
+        }
+
         return commandResult.stdout.toString() !== '';
     }