feat: add weth9 at old ovm eth address

packages/contracts/hardhat.config.ts

@@ -57,7 +57,14 @@ const config: HardhatUserConfig = {
     timeout: 50000,
   },
   solidity: {
-    version: '0.7.6',
+    compilers: [
+      {
+        version: '0.7.6',
+      },
+      {
+        version: '0.5.17', // Required for WETH9
+      },
+    ],
     settings: {
       optimizer: { enabled: true, runs: 200 },
       metadata: {

packages/contracts/src/predeploys.ts

@@ -21,4 +21,7 @@ export const predeploys = {
   // We're temporarily disabling OVM_ETH because the jury is still out on whether or not ETH as an
   // ERC20 is desirable.
   OVM_ETH: '0xDeadDeAddeAddEAddeadDEaDDEAdDeaDDeAD0000',
+
+  // We're also putting WETH9 at the old OVM_ETH address.
+  WETH9: '0x4200000000000000000000000000000000000006',
 }