gh-78630: Drop invalid HP aCC compiler switch -fPIC on HP-UX (#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.

setup.py

@@ -1408,9 +1408,6 @@ class PyBuildExt(build_ext):
             # finding some -z option for the Sun compiler.
             extra_link_args.append('-mimpure-text')
 
-        elif HOST_PLATFORM.startswith('hp-ux'):
-            extra_link_args.append('-fPIC')
-
         ext = Extension('_ctypes',
                         include_dirs=include_dirs,
                         extra_compile_args=extra_compile_args,