vswhere has a `-utf8` option

[zooba]

https://github.com/indygreg/python-build-standalone/blob/b292b16d25c61ac7dd962a4a4b52cd34724b33f6/cpython-windows/build.py#L235-L236

If you also pass the -utf8 option to vswhere, you can be guaranteed that it will write out a UTF-8 formatted path.