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

❌ Patch coverage is 1.47059% with 67 lines in your changes missing coverage. Please review.
✅ Project coverage is 28.27%. Comparing base (6089d04) to head (e4e7cee).

Files with missing lines	Patch %	Lines
src/compiler/compiler.rs	1.47%	67 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (6089d04) and HEAD (e4e7cee). Click for more details.

HEAD has 11 uploads less than BASE

Flag	BASE (6089d04)	HEAD (e4e7cee)
	14	3

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2825       +/-   ##
===========================================
- Coverage   76.22%   28.27%   -47.95%     
===========================================
  Files          72       71        -1     
  Lines       39890    36761     -3129     
===========================================
- Hits        30406    10396    -20010     
- Misses       9484    26365    +16881     

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[sylvestre]

please fix the conflict

[Joldiges]

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

Done, thank you

Accidentally done in 2 pushes. Sorry about that and the extra CI time/cost consumed