Upstream patch `patch-tkinter-3.13.patch` [Relocatable]

[`patch-tkinter-3.13.patch`](https://github.com/astral-sh/python-build-standalone/blob/main/cpython-unix/patch-tkinter-3.13.patch)

On Windows, CPython looks for Tcl/Tk libraries relative to the base prefix. On Unix, it doesn't.

This patch applies similar Windows-like behavior on Unix, ensuring Tcl/Tk libraries are found in the correct location relative to the installation.

**Related:**
- [`patch-tkinter-3.10.patch`](https://github.com/astral-sh/python-build-standalone/blob/main/cpython-unix/patch-tkinter-3.10.patch) (for Python 3.10)
- [`patch-tkinter-3.11.patch`](https://github.com/astral-sh/python-build-standalone/blob/main/cpython-unix/patch-tkinter-3.11.patch) (for Python 3.11)
- [`patch-tkinter-3.12.patch`](https://github.com/astral-sh/python-build-standalone/blob/main/cpython-unix/patch-tkinter-3.12.patch) (for Python 3.12)