feat(generator): replace length check with custom b-type

This messes up the function signature in ghidra

codegen/generate.py

@@ -99,9 +99,7 @@ def main():
 static volatile uint8_t MANGLED[] = "{mangled_secret}";
 
 bool check(char* userflag, uint8_t len) {{
-    if (len != {len(secret)}) {{
-        return false;
-    }}
+    custom_jmp_neq(len ^ 0x7C, {len(secret)}, label_false);
 
     {check}