Make oom-heap.c test work with newer GCC

[SvizelPritula]

This pull request fixes the oom-heap (C11 / gcc) test.

New GCC versions can optimize the old version of the test to use practically zero memory.

[codecov[bot]]

Codecov Report

Merging #1210 (de65a51) into master (0401c53) will decrease coverage by 30.23%. The diff coverage is n/a.

@@             Coverage Diff             @@
##           master    #1210       +/-   ##
===========================================
- Coverage   63.86%   33.63%   -30.24%     
===========================================
  Files         233      233               
  Lines       17151    17151               
===========================================
- Hits        10954     5768     -5186     
- Misses       6197    11383     +5186     

Flag	Coverage Δ
functionaltests	?
unittests	33.63% <ø> (-10.40%)	:arrow_down:

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Impacted Files	Coverage Δ
cms/server/admin/__init__.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/grading/scoretypes/Sum.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/server/contest/printing.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/server/contest/tokening.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/grading/scoretypes/GroupMin.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/grading/scoretypes/GroupMul.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/server/contest/communication.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/server/contest/authentication.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/server/admin/handlers/__init__.py	0.00% <0.00%> (-100.00%)	:arrow_down:
cms/server/contest/submission/check.py	0.00% <0.00%> (-100.00%)	:arrow_down:
... and 112 more

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