Ensure correct flags are passed to solc in std json mode (#440)

This tests the marketplace contracts to compile fine. In prior versions
this fails to compile, hitting the solc "Stack too deep" error.

Closes #409

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/integration/codesize.json

@@ -2,7 +2,7 @@
   "Baseline": 911,
   "Computation": 2337,
   "DivisionArithmetics": 14488,
-  "ERC20": 17041,
+  "ERC20": 17189,
   "Events": 1672,
   "FibonacciIterative": 1454,
   "Flipper": 2106,