HPCC-9432  use 'cat' not 'echo' Std,System.Util.CmdProcess in the example

Signed-off-by: Richard Taylor <richard.taylor@lexisnexis.com>
Merge pull request #4465 from RichardTaylorHPCC/B9432

HPCC-9432  use 'cat' not 'echo' Std,System.Util.CmdProcess in the exampl...

Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>