misc: check if permutations can be skipped at any point

src/main.c

@@ -302,6 +302,10 @@ int main(int argc, char *argv[]) {
             while (!a_out_perms[a_out - 1].exhausted) {
               ResetConditionalPermutations(b_out_perms, b_out);
               while (!b_out_perms[b_out - 1].exhausted) {
+                if (seen[lhs_i]) {
+                  goto skip_permutations;
+                }
+
                 // Compare the two rows
                 FromCgToP(a_out, b_out, a_in, b_in, rhs, p_buf,
                           a_in_perm.permutation, b_in_perm.permutation,