Make compiling with DEBUG actually work

[tautschnig]

Various places use #ifdef DEBUG, which we don't experiment with on a
regular basis. Fix syntax errors that crept in over time.

This is the result of actually enabling -DDEBUG by accident, I do not see real value in testing this in CI for we don't even use the same macro in all places.

• Each commit message has a non-empty body, explaining why the change was made.
• n/a Methods or procedures I have added are documented, following the guidelines provided in CODING_STANDARD.md.
• n/a 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).
• n/a My commit message includes data points confirming performance improvements (if claimed).
• My PR is restricted to a single feature or bugfix.
• n/a White-space or formatting changes outside the feature-related changed lines are in commits of their own.

[codecov]

Codecov Report

Merging #6848 (6baffa3) into develop (3df1868) will increase coverage by 0.74%.
The diff coverage is 88.96%.

@@             Coverage Diff             @@
##           develop    #6848      +/-   ##
===========================================
+ Coverage    77.04%   77.79%   +0.74%     
===========================================
  Files         1594     1567      -27     
  Lines       185287   179707    -5580     
===========================================
- Hits        142763   139797    -2966     
+ Misses       42524    39910    -2614     

Impacted Files	Coverage Δ
jbmc/src/jbmc/jbmc_parse_options.cpp	76.51% <ø> (+0.53%)	⬆️
...riable-sensitivity/variable_sensitivity_domain.cpp	90.00% <ø> (ø)
src/cbmc/cbmc_parse_options.cpp	79.90% <ø> (+0.87%)	⬆️
src/goto-instrument/accelerate/accelerate.cpp	31.94% <ø> (ø)
.../goto-instrument/accelerate/acceleration_utils.cpp	2.22% <ø> (ø)
src/goto-instrument/accelerate/trace_automaton.cpp	0.00% <ø> (ø)
src/goto-instrument/cover_basic_blocks.h	100.00% <ø> (ø)
src/goto-instrument/source_lines.h	100.00% <ø> (ø)
src/goto-instrument/unwind.h	100.00% <ø> (ø)
src/goto-instrument/wmm/data_dp.cpp	75.71% <ø> (ø)
... and 90 more

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