enable optimizations in foundry.toml and fix ci

keccak256_op was optimized to return(0, 0), which does not revert, which caused the test to fail

for context, newer foundry versions have the optimizer turned off (but ci uses the stable channel of foundry, which still has the optimizer turned on by default)

Author: 0xkarmacoma

tests/regression/foundry.toml

@@ -5,6 +5,8 @@ libs = ['../lib', 'lib']
 
 evm_version = 'cancun'
 
+optimizer = true
+
 force = false
 # compile options used by halmos (to prevent unnecessary recompilation when running forge test and halmos together)
 extra_output = ["storageLayout", "metadata"]

tests/regression/test/MegaMem.t.sol

@@ -76,10 +76,13 @@ contract MegaMemTest is Test, SymTest {
         }
     }
 
-    function keccak256_op(uint256 ptr, uint256 len) public pure {
+
+    function keccak256_op(uint256 ptr, uint256 len) public pure returns (bytes32) {
+        bytes32 hash;
         assembly {
-            let hash := keccak256(ptr, len)
+            hash := keccak256(ptr, len)
         }
+        return hash;
     }
 
     function mcopy(uint256 dst_ptr, uint256 src_ptr, uint256 src_len) public pure {