Link libpython for AIX target (#4073)

Author: messense

newsfragments/4073.fixed.md

@@ -0,0 +1 @@
+fixes undefined symbol errors when building extension module on AIX by linking `libpython`

pyo3-build-config/src/impl_.rs

@@ -775,6 +775,8 @@ pub fn is_linking_libpython() -> bool {
 /// Must be called from a PyO3 crate build script.
 fn is_linking_libpython_for_target(target: &Triple) -> bool {
     target.operating_system == OperatingSystem::Windows
+        // See https://github.com/PyO3/pyo3/issues/4068#issuecomment-2051159852
+        || target.operating_system == OperatingSystem::Aix
         || target.environment == Environment::Android
         || target.environment == Environment::Androideabi
         || !is_extension_module()