[CI] Add a linux+clang+make github actions job.

[NlightNFotis]

This replaces a codebuild job that had not been ported yet,
so that codebuild can be safely deactivated as a CI provider,
having all the configurations ported so far.

• Each commit message has a non-empty body, explaining why the change was made.
• Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• 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.
• White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[thomasspriggs]

👍

[thomasspriggs]

❔ Do we need gcc gdb g++ for a clang build?

[NlightNFotis]

I thought about it - I opted for keeping the job's environment in line with the linux+make+gcc one.

Though these are arguably not very useful given that they are preinstalled in Github runners. But I suggest this stays for now and we have a separate discussion on whether we should remove them from the other build as well.

[piotr-grabalski]

looks good to me

[codecov]

Codecov Report

Merging #5559 (81ecf05) into develop (e5e8239) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #5559      +/-   ##
===========================================
- Coverage    72.85%   72.84%   -0.01%     
===========================================
  Files         1421     1421              
  Lines       154130   154138       +8     
===========================================
- Hits        112292   112289       -3     
- Misses       41838    41849      +11     

Impacted Files	Coverage Δ
src/solvers/flattening/bv_pointers.cpp	80.89% <0.00%> (-2.05%)	⬇️
src/solvers/flattening/bv_pointers.h	100.00% <0.00%> (ø)

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[tautschnig]

Please also make sure we port all the features of the CodeBuild jobs. Specifically, the "cbmc" CodeBuild job is running with _GLIBCXX_DEBUG, which we don't seem to be doing in any of the GitHub actions just yet.

Also, I am wondering about the use of ccache to speed up builds? (done)