Fix DCE symbol name logic on macOS

Only use the private Apple symbol name for the DCE extension detection
when using the actual GSS.Framework target. This will allow compiling
this library against a custom MIT krb5 or Heimdal library on macOS with
support for the normal IOV wrapping functions.

Signed-off-by: Jordan Borean <[email protected]>

setup.py

@@ -156,6 +156,7 @@ def get_output(*args, **kwargs):
 ENABLE_SUPPORT_DETECTION = \
     (os.environ.get('GSSAPI_SUPPORT_DETECT', 'true').lower() == 'true')
 
+wrap_iov_symbol_name = 'gss_wrap_iov'
 if ENABLE_SUPPORT_DETECTION:
     import ctypes.util
 
@@ -205,6 +206,9 @@ def get_output(*args, **kwargs):
 
     GSSAPI_LIB = ctypes.CDLL(os.path.join(main_path, main_lib))
 
+    if hasattr(GSSAPI_LIB, '__ApplePrivate_gss_wrap_iov'):
+        wrap_iov_symbol_name = '__ApplePrivate_gss_wrap_iov'
+
 
 def make_extension(name_fmt, module, **kwargs):
     """Helper method to remove the repetition in extension declarations."""
@@ -323,9 +327,7 @@ def gssapi_modules(lst):
         extension_file('rfc5588', 'gss_store_cred'),
         extension_file('rfc5801', 'gss_inquire_saslname_for_mech'),
         extension_file('cred_imp_exp', 'gss_import_cred'),
-        extension_file('dce',
-                       '__ApplePrivate_gss_wrap_iov' if osx_has_gss_framework
-                       else 'gss_wrap_iov'),
+        extension_file('dce', wrap_iov_symbol_name),
         extension_file('dce_aead', 'gss_wrap_aead'),
         extension_file('iov_mic', 'gss_get_mic_iov'),
         extension_file('ggf', 'gss_inquire_sec_context_by_oid'),