[OMPT] Fix null pointer in parallel/no_thread_num_clause.c

Looks like the implementation of printf on Darwin uses "0x0"
instead of "(nil)" like glibc does.

git-svn-id: https://llvm.org/svn/llvm-project/openmp/trunk@317515 91177308-0d34-0410-b5e6-96231b3b80d8

runtime/test/ompt/parallel/no_thread_num_clause.c

@@ -51,7 +51,7 @@ int main()
 
   // THREADS: 0: NULL_POINTER=[[NULL:.*$]]
   // THREADS: {{^}}[[MASTER_ID:[0-9]+]]: ompt_event_thread_begin: thread_type=ompt_thread_initial=1, thread_id=[[MASTER_ID]]
-  // THREADS: {{^}}[[MASTER_ID]]: ompt_event_task_create: parent_task_id=0, parent_task_frame.exit=(nil), parent_task_frame.reenter=(nil), new_task_id=281474976710658, codeptr_ra=(nil), task_type=ompt_task_initial=1, has_dependences=no
+  // THREADS: {{^}}[[MASTER_ID]]: ompt_event_task_create: parent_task_id=0, parent_task_frame.exit=[[NULL]], parent_task_frame.reenter=[[NULL]], new_task_id=281474976710658, codeptr_ra=[[NULL]], task_type=ompt_task_initial=1, has_dependences=no
   // THREADS: {{^}}[[MASTER_ID]]: ompt_event_parallel_begin: parent_task_id=[[PARENT_TASK_ID:[0-9]+]], parent_task_frame.exit=[[NULL]], parent_task_frame.reenter={{0x[0-f]+}}, parallel_id=[[PARALLEL_ID:[0-9]+]], requested_team_size=4, codeptr_ra=[[RETURN_ADDRESS:0x[0-f]+]]{{[0-f][0-f]}}, invoker={{[0-9]+}}
 
   // THREADS: {{^}}[[MASTER_ID]]: ompt_event_implicit_task_begin: parallel_id=[[PARALLEL_ID]], task_id=[[IMPLICIT_TASK_ID:[0-9]+]]