Compile CaDiCaL with -DNDEBUG

[tautschnig]

Using CaDiCaL with CBMC showed substantially decreased performance between versions 1.8.0 and 1.9.0. This has become apparent with Kani, but also our THOROUGH tests changed from 7 minutes to just under 2 hours in CI. The culprit is
arminbiere/cadical@69e7cfb, which introduces expensive checks in NDEBUG blocks.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a The feature or user visible behaviour I have added or modified has been documented in the User Guide in doc/cprover-manual/
• Regression or unit tests are included, or existing tests cover the modified code (in this case I have detailed which ones those are in the commit message).
• My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.02%. Comparing base (bf58af8) to head (c0fd50b).
Report is 2 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #8397      +/-   ##
===========================================
- Coverage    78.02%   78.02%   -0.01%     
===========================================
  Files         1726     1726              
  Lines       189432   189442      +10     
  Branches     18465    18466       +1     
===========================================
+ Hits        147807   147808       +1     
- Misses       41625    41634       +9     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.