Upstream patch `patch-python-relative-build-details.patch`

[`patch-python-relative-build-details.patch`](https://github.com/astral-sh/python-build-standalone/blob/main/cpython-unix/patch-python-relative-build-details.patch)

The new build-details.json file in Python 3.14+ can contain absolute paths from the build environment.

This patch ensures build-details.json reports relocatable paths instead.