Compile CaDiCaL with -DNDEBUG

Using CaDiCaL with CBMC showed substantially decreased performance
between versions 1.8.0 and 1.9.0. This has become apparent with Kani,
but also our THOROUGH tests changed from 7 minutes to just under 2 hours
in CI. The culprit is
arminbiere/cadical@69e7cfb,
which introduces expensive checks in `NDEBUG` blocks.

Author: tautschnig

scripts/cadical_CMakeLists.txt

@@ -9,7 +9,7 @@ add_library(cadical ${sources})
 
 # Pass -DNBUILD to disable including the version information, which is not
 # needed since cbmc doesn't run the cadical binary
-target_compile_options(cadical PUBLIC -DNBUILD -DNFLEXIBLE)
+target_compile_options(cadical PUBLIC -DNBUILD -DNFLEXIBLE -DNDEBUG)
 
 set_target_properties(
     cadical

src/solvers/Makefile

@@ -281,7 +281,7 @@ solvers$(LIBEXT): $(OBJ) $(SOLVER_LIB)
 	$(LINKLIB)
 
 ../../cadical/build/libcadical$(LIBEXT):
-	$(MAKE) $(MAKEARGS) -C $(CADICAL)/build libcadical.a CXX="$(CXX)" CXXFLAGS="$(CP_CXXFLAGS) -DNFLEXIBLE"
+	$(MAKE) $(MAKEARGS) -C $(CADICAL)/build libcadical.a CXX="$(CXX)" CXXFLAGS="$(CP_CXXFLAGS) -DNFLEXIBLE -DNDEBUG"
 
 -include smt2/smt2_solver$(DEPEXT)