Deduce nonzero returncode from eclrun std output

[berland]

runeclipse from subscript was used for this earlier, and this had code to parse the stdout/stderr files for Error counts.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.16%. Comparing base (7477100) to head (cc922a2).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #772   +/-   ##
=======================================
  Coverage   85.16%   85.16%           
=======================================
  Files          52       52           
  Lines        7421     7421           
=======================================
  Hits         6320     6320           
  Misses       1101     1101           

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