Load versioned libz3 soname in Python bindings on Linux (#10290)

The generated Python bindings loaded `libz3.so` without a soversion,
which could bind to an ABI-incompatible shared library when multiple Z3
versions are present. This change makes Linux bindings prefer the
versioned soname while leaving other platforms on the existing lookup
path.

- **Python loader generation**
  - Thread a `z3py_soversion` parameter through `scripts/update_api.py`.
- Generate `_lib_name` as `libz3.so.<major>.<minor>` on Linux, and keep
`libz3.<ext>` elsewhere.
- Reuse `_lib_name` consistently for directory probing, system fallback,
and error messages.

- **Build-system wiring**
- Pass the current `SOVERSION` from the CMake Python bindings build on
Linux.
- Pass the same value through the `mk_make`/`mk_util.py` generation path
so both build systems emit the same loader behavior.

- **In-tree Python bindings layout**
- Add the matching `libz3.so.<major>.<minor>` link in `build/python/` on
Linux so the generated bindings work directly from the build tree.

- **Regression coverage**
- Add a focused script-level test for the generated loader preamble to
check:
    - Linux uses the versioned soname when provided.
- Non-versioned fallback remains available when no soversion is
supplied.

Example of the generated Linux loader behavior:

```python
_sover = '5.0'
_ext = 'so'
_lib_name = 'libz3.%s.%s' % (_ext, _sover) if sys.platform.startswith('linux') and _sover else 'libz3.%s' % _ext
_lib = ctypes.CDLL(_lib_name)
```

<!-- START COPILOT CODING AGENT SUFFIX -->

- Fixes #7518

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: NikolajBjorner <3085284+NikolajBjorner@users.noreply.github.com>
Co-authored-by: Nikolaj Bjorner <nikolaj@cs.stanford.edu>

src/api/python/CMakeLists.txt

@@ -20,6 +20,13 @@ set(z3py_bindings_build_dest "${PROJECT_BINARY_DIR}/python")
 file(MAKE_DIRECTORY "${z3py_bindings_build_dest}")
 file(MAKE_DIRECTORY "${z3py_bindings_build_dest}/z3")
 
+set(z3py_soversion_args "")
+if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+  set(z3py_soversion_args
+    "--z3py-soversion"
+    "${Z3_VERSION_MAJOR}.${Z3_VERSION_MINOR}")
+endif()
+
 set(build_z3_python_bindings_target_depends "")
 foreach (z3py_file ${z3py_files})
   add_custom_command(OUTPUT "${z3py_bindings_build_dest}/${z3py_file}"
@@ -37,6 +44,7 @@ add_custom_command(OUTPUT "${z3py_bindings_build_dest}/z3/z3core.py"
   COMMAND "${Python3_EXECUTABLE}"
     "${PROJECT_SOURCE_DIR}/scripts/update_api.py"
     ${Z3_FULL_PATH_API_HEADER_FILES_TO_SCAN}
+    ${z3py_soversion_args}
     "--z3py-output-dir"
     "${z3py_bindings_build_dest}"
   DEPENDS
@@ -93,6 +101,17 @@ if (TARGET libz3)
     DEPENDS ${LIBZ3_DEPENDS}
     COMMENT "Linking libz3 into python directory"
   )
+  if (CMAKE_SYSTEM_NAME STREQUAL "Linux")
+    add_custom_command(OUTPUT "${z3py_bindings_build_dest}/libz3${CMAKE_SHARED_MODULE_SUFFIX}.${Z3_VERSION_MAJOR}.${Z3_VERSION_MINOR}"
+      COMMAND "${CMAKE_COMMAND}" "-E" "${LINK_COMMAND}"
+        "${LIBZ3_SOURCE_PATH}"
+        "${z3py_bindings_build_dest}/libz3${CMAKE_SHARED_MODULE_SUFFIX}.${Z3_VERSION_MAJOR}.${Z3_VERSION_MINOR}"
+      DEPENDS ${LIBZ3_DEPENDS}
+      COMMENT "Linking versioned libz3 into python directory"
+    )
+    list(APPEND build_z3_python_bindings_target_depends
+      "${z3py_bindings_build_dest}/libz3${CMAKE_SHARED_MODULE_SUFFIX}.${Z3_VERSION_MAJOR}.${Z3_VERSION_MINOR}")
+  endif()
 else()
   message(FATAL_ERROR "libz3 target not found. Cannot build Python bindings.")
 endif()