finish tool can use 'nimgrab' tool to download the mingw version

tools/nimgrab.nim

@@ -0,0 +1,17 @@
+
+import os, asyncdispatch, httpclient
+
+proc syncDownload(url, file: string) =
+  var client = newHttpClient()
+  proc onProgressChanged(total, progress, speed: BiggestInt) =
+    echo "Downloading " & url & " " & $(speed div 1000) & "kb/s"
+    echo clamp(int(progress*100 div total), 0, 100), "%"
+
+  client.onProgressChanged = onProgressChanged
+  client.downloadFile(url, file)
+  echo "100%"
+
+if os.paramCount() != 2:
+  quit "Usage: nimgrab <url> <file>"
+else:
+  syncDownload(os.paramStr(1), os.paramStr(2))