gh-78630: Drop invalid HP aCC compiler switch -fPIC on HP-UX (GH-8847)

At compile time, '+z' is already properly used with HP aCC, and shared
libraries are correctly linked with '+b'. The '-fPIC' switch can safely be
dropped.
(cherry picked from commit 09be18a73d81aa82cc57a782f3b0a9811e43ad3b)

Co-authored-by: Michael Osipov <michael.osipov@siemens.com>