fix: regex works incorrectly when using -c option

[quentin]

Make sure the c++ code generator emits raw string literals.

fixes #2532

[codecov]

Codecov Report

Attention: Patch coverage is 72.22222% with 10 lines in your changes missing coverage. Please review.

Project coverage is 81.10%. Comparing base (8ed1d22) to head (3a833b0).
Report is 2 commits behind head on master.

Files with missing lines	Patch %	Lines
src/synthesiser/Synthesiser.cpp	72.22%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2534      +/-   ##
==========================================
+ Coverage   81.09%   81.10%   +0.01%     
==========================================
  Files         492      492              
  Lines       33368    33369       +1     
==========================================
+ Hits        27059    27064       +5     
+ Misses       6309     6305       -4     

Files with missing lines	Coverage Δ
src/synthesiser/Synthesiser.cpp	85.05% <72.22%> (+0.01%)	⬆️

... and 4 files with indirect coverage changes

🚀 New features to boost your workflow:

• ❄ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.