ada: Fix regression of finalization primitive selection

A recent patch introduced a new flag to mark the types for which looking
up finalization primitives needs special handling. But there was one
place in Build_Derived_Record_Type where the flag was not set when it
should, which introduced a regression in some cases.

This patch adds the missing setting of the flag.

gcc/ada/ChangeLog:

	* sem_ch3.adb (Build_Derived_Record_Type): Set flag appropriately.

Author: ronan-d

gcc/ada/sem_ch3.adb

@@ -9660,6 +9660,8 @@ package body Sem_Ch3 is
            (New_Decl, Parent_Base, New_Base,
             Is_Completion => False, Derive_Subps => False);
 
+         Set_Is_Implicit_Full_View (New_Base);
+
          --  ??? This needs re-examination to determine whether the
          --  following call can simply be replaced by a call to Analyze.