```cmake
# This extends CMake's FindHDF5.cmake to add support to include MPI include
# paths and libraries in the HDF5 ones if HDF5_IS_PARALLEL is ON
# (BUG #0014363).

# include the default FindHDF5.cmake.
include(${CMAKE_ROOT}/Modules/FindHDF5.cmake)

if(HDF5_FOUND AND HDF5_IS_PARALLEL)
  include(vtkMPI)
  if(MPI_C_INCLUDE_PATH)
    list(APPEND HDF5_INCLUDE_DIRS ${MPI_C_INCLUDE_PATH})
  endif()
  if(MPI_C_LIBRARIES)
    list(APPEND HDF5_LIBRARIES ${MPI_C_LIBRARIES})
  endif()
endif()
```

Fix issue with external HDF5
user
```cmake
# This extends CMake's FindHDF5.cmake to add support to include MPI include
# paths and libraries in the HDF5 ones if HDF5_IS_PARALLEL is ON
# (BUG #0014363).

# include the default FindHDF5.cmake.
include(${CMAKE_ROOT}/Modules/FindHDF5.cmake)

if(HDF5_FOUND AND (HDF5_IS_PARALLEL OR HDF5_ENABLE_PARALLEL))
  include(vtkMPI)
  if(MPI_C_INCLUDE_PATH)
    list(APPEND HDF5_INCLUDE_DIRS ${MPI_C_INCLUDE_PATH})
  endif()
  if(MPI_C_LIBRARIES)
    list(APPEND HDF5_LIBRARIES ${MPI_C_LIBRARIES})
  endif()
endif()
```
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