Auto merge of #118789 - jyn514:dry-run, r=onur-ozkan

fix --dry-run when the change-id warning is printed

previously:
```
Building bootstrap
   Compiling bootstrap v0.0.0 (/home/jyn/src/rust2/src/bootstrap)
    Finished dev [unoptimized] target(s) in 4.23s
thread 'main' panicked at src/bin/main.rs:147:17:
fs::write(warned_id_path, latest_change_id.to_string()) failed with No such file or directory (os error 2)
```

Author: bors