Forward target options during detection

[Joldiges]

Compiler identification runs a preprocessing probe without preserving target selection. Clang-compatible cross-compilers that require an explicit target can therefore fail detection before a compilation is considered for caching.

Forward GNU/Clang --target and -target options into the detection probe, including values supplied through response files. Normalize single-dash -target to the separated form accepted by standard Clang and add coverage for all joined and separated forms.

This change was primarily made to fix an assumed regression in v0.17 where informing SCcache that ARM-Clang was Clang-like was now failing

GitHub copilot was used for the debugging and resolution of this issue.

[Copilot]

Pull request overview

This PR fixes C/C++ compiler vendor detection for Clang-compatible cross-compilers by forwarding target-selection flags into the preprocessing probe used during detection (including when those flags come from @response files). This prevents detection failures when a compiler requires an explicit target to run even in -E mode.

Changes:

• Forward --target and -target (including joined/separated spellings) into the compiler detection probe.
• Expand @response files during detection argument scanning so target flags provided via response files are preserved.
• Add unit tests covering forwarding and normalization behavior for --target/-target, including response-file input.

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 70.11%. Comparing base (8ab3926) to head (3dac588).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2825      +/-   ##
==========================================
- Coverage   73.71%   70.11%   -3.61%     
==========================================
  Files          72       72              
  Lines       37932    37966      +34     
==========================================
- Hits        27963    26620    -1343     
- Misses       9969    11346    +1377     

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