Fix stdin for casr-libafl

[headshog]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 88.88889% with 1 line in your changes missing coverage. Please review.

Project coverage is 66.46%. Comparing base (840145d) to head (ccf5484).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
casr/src/bin/casr-libfuzzer.rs	88.88%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #243      +/-   ##
==========================================
+ Coverage   66.45%   66.46%   +0.01%     
==========================================
  Files          34       34              
  Lines        8179     8185       +6     
==========================================
+ Hits         5435     5440       +5     
- Misses       2744     2745       +1     

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