Fixing intermittent test failures

[secure-sw-dev-bot]

This issue was copied from checkedc/checkedc-clang#860

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Reference: checkedc/checkedc-clang#854

We fixed root cause memory corruption and enabled all the tests.

[secure-sw-dev-bot]

Comment from @mgrang:

Thanks for the fix. I have verified the fix with a Windows X86 ADO build: https://dev.azure.com/msresearch/CheckedC/_build/results?buildId=513155&view=results