Switch poly_tomsg CBMC proof to smt2

This seems faster than bitwuzla.

Signed-off-by: Hanno Becker <[email protected]>

cbmc/proofs/poly_frommsg/Makefile

@@ -25,7 +25,7 @@ USE_DYNAMIC_FRAMES=1
 
 # Disable any setting of EXTERNAL_SAT_SOLVER, and choose SMT backend instead
 EXTERNAL_SAT_SOLVER=
-CBMCFLAGS=--bitwuzla
+CBMCFLAGS=--smt2
 
 FUNCTION_NAME = $(MLKEM_NAMESPACE)poly_frommsg