Get a proper path to the python shared library for the QPD plugin

[maliasadi]

Context:
The current get_libpython_path() trusts LDLIBRARY, and if it finds nothing, then it returns an empty string. This causes the QPD plugin fails on envs when LDLIBRARY sets to the static archived python library instead of the shared one (e.g., on conda envs: LDLIBRARY = libpython3.14.a).

This PR fixes this with a minimal patch to get_libpython_path() that it now only accepts LDLIBRARY when it's actually a shared object, and otherwise falls back to the conventional libpython{LDVERSION}.so in LIBDIR, then a glob of libpython*.so*. This fixes the issues on conda envs while preserving the current behaviour on other envs.

Benefits:

• Fix the QPD plugin on conda envs.

Possible Drawbacks:
n/a

Related GitHub Issues:

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