Shard the long-running CORE runs of contracts-dfcc and jbmc-strings

[tautschnig]

These two suites are the slowest non-sharded CORE ctest entries and, at a single 30-minute-capped test each, intermittently time out on the slower and highly variable macOS-14 runners (their per-run time there swings roughly 2-3x). Their timeouts (1800s) are already above the 1200s default, so the right remedy is sharding rather than a further timeout bump.

Split each suite's CORE profile into 4 parallel shards via test.pl's --shard option, reusing the add_sharded_test_pl_profile helper already used for the jbmc-strings symex-driven-lazy-loading profile. The smaller pieces run in parallel as separate ctest entries instead of one indivisible test, so they no longer dominate the job wall-clock or approach the per-test timeout. Each shard keeps the suite's previous 30-minute cap, which is now ample headroom.

The contracts-dfcc smt2_solver PATH environment is applied to each shard, and the THOROUGH/FUTURE/KNOWNBUG levels remain single tests.

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[Copilot]

Pull request overview

This PR reduces wall-clock time and intermittent macOS runner timeouts by sharding two long-running regression suites’ CORE ctest entries into multiple parallel shards, using the existing add_sharded_test_pl_profile helper.

Changes:

• Shard contracts-dfcc CORE into 4 parallel ctest tests (each retaining the previous 1800s timeout), and apply the smt2_solver PATH environment to each shard.
• Shard jbmc-strings CORE into 4 parallel ctest tests (each retaining the previous 1800s timeout), mirroring the already-sharded symex-driven profile.
• Broaden JBMC regression log ignore pattern to cover shard log filenames (tests-*.log).

Reviewed changes

Copilot reviewed 2 out of 3 changed files in this pull request and generated no comments.

File	Description
regression/contracts-dfcc/CMakeLists.txt	Replaces a single long CORE test with 4 sharded CORE tests (plus explicit THOROUGH/FUTURE/KNOWNBUG), and applies the smt2_solver PATH env to each shard.
jbmc/regression/jbmc-strings/CMakeLists.txt	Converts the suite’s CORE run into 4 shards using add_sharded_test_pl_profile, while keeping other levels as single tests.
.gitignore	Ignores JBMC shard log files via jbmc/regression/**/tests-*.log.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.69%. Comparing base (02c2769) to head (4cd5fce).

Additional details and impacted files

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##           develop    #9086   +/-   ##
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  Coverage    80.69%   80.69%           
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  Files         1714     1714           
  Lines       189597   189597           
  Branches        73       73           
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+ Hits        152987   152988    +1     
+ Misses       36610    36609    -1     

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