In configure.ac the config is still tuned for HP-UX on PA-RISC which is dead for many many years. Attached you'll find a patch to properly link with HP-UX on IA64:

• Shared libs on IA64 are -- by default -- .so
• The default way to link is to use the compiler -- as advised by HPE support

The patch has been produced against 9.11.6.bind9.patch