Fix stream did not contain valid UTF-8 (#8120)
## Summary
Related issues: #8009 #7549
Although `PYTHONIOENCODING=utf-8` forces python to use UTF-8 for
`stdout`/`stderr`, it can't prevent code like
`sys.stdout.buffer.write()` or `subprocess.call(["cl.exe", ...])` to
bypass the encoder. This PR uses lossy UTF-8 conversion to avoid
decoding error.
## Alternative
Using `bstr` crate might be better since it can preserve original
information. Or we should follow the Windows convention, unset
`PYTHONIOENCODING` and decode with system default encoding.
## Test Plan
Running locally with non-ASCII character in `UV_CACHE_DIR` works fine,
but I have no unit test plan. Testing locale problem is hard :(
