Document vfork known issue. am: 9c7a8fbc59
Document vfork known issue. am: 9c7a8fbc59

Original change: https://android-review.googlesource.com/c/platform/external/perfetto/+/1343516

Change-Id: Ifc1e1a28110aab9d134fafad4de73101b4056f77

google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto,google/perfetto