[Offload] [OMPT] Fixed missing trace records in ompt_flush_trace. (llvm#1590)

Author: Salinas, David

offload/src/OpenMP/OMPT/OmptTracingBuffer.cpp

@@ -507,6 +507,11 @@ OmptTracingBufferMgr::findAndReserveFlushedBuf(uint64_t flush_id) {
   }
   assert(flush_itr->second.FlushStatus == Flush_waiting);
   flush_itr->second.FlushStatus = Flush_processing;
+  // Update the metadata cursor since more trace records may have been
+  // generated.
+  flush_itr->second.FlushCursor =
+      flush_itr->second.FlushBuf->Cursor.load(std::memory_order_acquire);
+
   FlushInfo flush_info(flush_itr->first, flush_itr->second.FlushCursor,
                        flush_itr->second.FlushBuf);
   DP("Reserved buffer: flush_id:%lu, cursor:%p, buf:%p\n", flush_itr->first,