Can't patch source anymore

In `conda-launchers`, we need to patch this [C source file](https://raw.githubusercontent.com/python/cpython/3.7/PC/launcher.c) with [this diff](https://github.com/conda/conda-launchers/blob/9d9ad851cd042583020c574f86b60fd9e61a090a/src/cpython-launcher-c-mods-for-setuptools.3.7.patch). This used to work (as of Dec 2025, [CI could pass](https://github.com/conda/conda-launchers/pull/16)), but not [anymore](https://github.com/conda/conda-launchers/pull/18). IIRC recent versions of rattler-build changed their diff engine?