Contracts (DFCC) regression tests: use CaDiCaL

Using CaDiCaL as SAT solver (when available) instead of MiniSat reduces
test execution time from 337 seconds down to 131 seconds (with only a
single test now taking more than 2 seconds, where its 6 seconds are
mainly spent in symex).

regression/contracts-dfcc/chain.sh

@@ -59,4 +59,4 @@ elif echo $args_inst | grep -q -- "--dump-c" ; then
   rm "${name}${dfcc_suffix}-mod.c"
 fi
 $goto_instrument --show-goto-functions "${name}${dfcc_suffix}-mod.gb"
-$cbmc "${name}${dfcc_suffix}-mod.gb" ${args_cbmc}
+$cbmc --sat-solver cadical "${name}${dfcc_suffix}-mod.gb" ${args_cbmc}