Fix malloc declaration in Linked_List1 regression test

[tautschnig]

We had invalid pointers instead of dynamic objects in this test, which
didn't matter to much. It may, however, matter with upcoming support for
non-deterministic pointers.

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[codecov]

Codecov Report

Merging #6492 (c13e416) into develop (5bf69a3) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #6492   +/-   ##
========================================
  Coverage    76.04%   76.04%           
========================================
  Files         1546     1546           
  Lines       165521   165543   +22     
========================================
+ Hits        125864   125885   +21     
- Misses       39657    39658    +1     

Impacted Files	Coverage Δ
src/goto-instrument/contracts/contracts.cpp	97.10% <100.00%> (+0.35%)	⬆️
unit/util/simplify_expr.cpp	99.66% <100.00%> (+0.01%)	⬆️
src/goto-instrument/loop_utils.cpp	82.85% <0.00%> (-8.58%)	⬇️

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[martin-cs]

Should that be size_t?

[martin-cs]

https://github.com/diffblue/cbmc/runs/4369109439?check_suite_focus=true looks like an interesting failure.

[tautschnig]

Should that be size_t?

We're not including any headers in this file, so I resorted to the frontend-provided internal type instead.

[tautschnig]

https://github.com/diffblue/cbmc/runs/4369109439?check_suite_focus=true looks like an interesting failure.

I have added this to my todo list (seems dump-c is not failing to do some cleanup).