Upstream patch `patch-sem-clockwait-weak-3.15.patch`

`patch-sem-clockwait-weak-3.15.patch`[https://github.com/astral-sh/python-build-standalone/blob/main/cpython-unix/patch-sem-clockwait-weak-3.15.patch]

Added in #895 to make the availability of `sem_clockwait` a run time detection rather than build time.

Start with cpython-unix/patch-sem-clockwait-weak-3.15.patch and the linked context from issue #895. Determine what upstream change or maintenance is expected for the sem_clockwait runtime-detection patch; done should be defined by the issue’s intended update and the relevant Python build checks passing.

Written by the indexing model from the issue text.