b/191084510. Update perf_event.h to has aux_size, to fix below error when building lldb on
linux:

llvm-project/lldb/source/Plugins/Process/Linux/IntelPTManager.cpp:53:23:
error: no member named 'aux_size' in 'perf_event_mmap_page'
  return m_mmap_meta->aux_size;
         ~~~~~~~~~~~~~^
-----
diff --git a/usr/include/linux/perf_event.h b/usr/include/linux/perf_event.h
index 1c749ee..606f875 100644
--- a/usr/include/linux/perf_event.h
+++ b/usr/include/linux/perf_event.h
@@ -433,6 +433,24 @@ struct perf_event_mmap_page {
 	 */
 	__u64   data_head;		/* head in the data section */
 	__u64	data_tail;		/* user-space written tail */
+	__u64	data_offset;		/* where the buffer starts */
+	__u64	data_size;		/* data buffer size */
+
+	/*
+	 * AUX area is defined by aux_{offset,size} fields that should be set
+	 * by the userspace, so that
+	 *
+	 *   aux_offset >= data_offset + data_size
+	 *
+	 * prior to mmap()ing it. Size of the mmap()ed area should be aux_size.
+	 *
+	 * Ring buffer pointers aux_{head,tail} have the same semantics as
+	 * data_{head,tail} and same ordering rules apply.
+	 */
+	__u64	aux_head;
+	__u64	aux_tail;
+	__u64	aux_offset;
+	__u64	aux_size;
 };
 
 #define PERF_RECORD_MISC_CPUMODE_MASK		(7 << 0)