warning: rustc_llvm@0.0.0: Compiler version doesn't include clang or GCC: "c++" "--version"

This happens when compiling rustc on Ubuntu 22.04. `c++ --version` shows:

```
c++ (Ubuntu 11.4.0-1ubuntu1~22.04) 11.4.0
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
```