Strip whitespace from FFI responses

Fixes #1129

Author: elopez

lib/Echidna/Exec.hs

@@ -160,7 +160,7 @@ execTxWith executeTx tx = do
         let process = (P.proc cmd args) { P.env = Just mergedEnv }
         (_, stdout, _) <- liftIO $ P.readCreateProcessWithExitCode process ""
         let encodedResponse = encodeAbiValue $
-              AbiTuple (V.fromList [AbiBytesDynamic . hexText . T.pack $ stdout])
+              AbiTuple (V.fromList [AbiBytesDynamic . hexText . T.strip . T.pack $ stdout])
         fromEVM (continuation encodedResponse)
         runFully
 

tests/solidity/cheat/ffi.sol

@@ -14,7 +14,7 @@ contract TestFFI {
     inputs[0] = "sh";
     inputs[1] = "-c";
     // ABI encoded "gm", as a string
-    inputs[2] = "printf '%s' '0x00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000002676d000000000000000000000000000000000000000000000000000000000000'";
+    inputs[2] = "echo '0x00000000000000000000000000000000000000000000000000000000000000200000000000000000000000000000000000000000000000000000000000000002676d000000000000000000000000000000000000000000000000000000000000'";
 
     bytes memory res = Hevm(HEVM_ADDRESS).ffi(inputs);