Run Windows test using --sequential

This brings our Windows testing setup in line with our other
testing setups.

make.ps1

@@ -217,8 +217,8 @@ switch ($Command.ToLower())
     }
 
     $testFile = (BuildTest)[-1]
-    Write-Host "$testFile"
-    & "$testFile"
+    Write-Host "$testFile --sequential"
+    & "$testFile" --sequential
     if ($LastExitCode -ne 0) { throw "Error" }
     break
   }