PEP517 backend is non-deterministic

## Long story short

We noticed in repro test that this package does not result in deterministic output. The problem is creation of temporary directory here https://github.com/aio-libs/frozenlist/blob/8c15ec9/packaging/pep517_backend/_backend.py#L199. It leaks into debuginfo (we spotted this through analysing _frozenlist.cpython-312-aarch64-linux-gnu.so.debug)

## Expected behaviour

Debuginfo is deterministic

## Actual behaviour

Debuginfo is not deterministic

## Steps to reproduce

Build twice, extract debuginfo, run diffoscope on data.

## Your environment

freedesktop-sdk.