Catch KeyboardInterupt in download_file

When interupting a download with something like control c the program will quit but won't clean it self up and will leave an invalid file. There is a handler for Exception, but this wont catch interupts. If you try to rerun the program it won't try to redownload it the next time.

emsdk

@@ -487,6 +487,10 @@ def download_file(url, dstpath, download_even_if_exists=False, filename_prefix =
     print("Error downloading URL '" + url + "': " + str(e))
     rmfile(file_name)
     return None
+  except KeyboardInterrupt as e:
+    print("Received Interrupt, exiting")
+    rmfile(file_name)
+    exit(0)
   return file_name
 
 def download_text_file(url, dstpath, download_even_if_exists=False, filename_prefix=''):