Auto merge of #112916 - tgross35:patch-1, r=Mark-Simulacrum

Add more context to `quit_if_file_exists` in `configure.py` & delete config.toml in CI

If the `obj` directory isn't empty, the error message is subtle and not very helpful:

```
== clock drift check ==
  local time: Sun Jul  2 00:57:06 UTC 2023
  network time: Sun, 02 Jul 2023 00:57:06 GMT
== end clock drift check ==
sccache: Starting the server...
configure: error: Existing 'config.toml' detected.
== clock drift check ==
  local time: Sun Jul  2 00:57:06 UTC 2023
  network time: Sun, 02 Jul 2023 00:57:06 GMT
== end clock drift check ==
```

This makes it stand out and suggests how to resolve the issue:

```
== clock drift check ==
  local time: Sun Jul  2 02:11:30 UTC 2023
  network time: Sun, 02 Jul 2023 02:11:31 GMT
== end clock drift check ==
sccache: Starting the server...

configure: ERROR: Existing 'config.toml' detected. Exiting
Is objdir '/home/tmgross/projects/rust/obj' clean?

== clock drift check ==
  local time: Sun Jul  2 02:11:31 UTC 2023
  network time: Sun, 02 Jul 2023 02:11:31 GMT
== end clock drift check ==
```

Author: bors