contracts: add a method for building legacy bindings

This will be useful for porting hh tasks to go because
hh runs out of memory. This creates a new bindings package
called `legacy`. There are no changes to the legacy contracts,
so we do not need to worry about checking for changes.

packages/contracts/package.json

@@ -22,6 +22,7 @@
   "scripts": {
     "build": "yarn build:contracts && yarn copy:contracts && yarn autogen:artifacts && yarn build:typescript",
     "build:typescript": "tsc -p ./tsconfig.json",
+    "build:bindings": "./scripts/legacy-bindings.sh ./../../op-bindings/legacy-bindings",
     "build:contracts": "hardhat compile --show-stack-traces",
     "autogen:markdown": "ts-node scripts/generate-markdown.ts",
     "autogen:artifacts": "ts-node scripts/generate-artifacts.ts && ts-node scripts/generate-deployed-artifacts.ts",

packages/contracts/scripts/legacy-bindings.sh

+#!/bin/bash
+
+OUTDIR="$1"
+
+if [ ! -d "$OUTDIR" ]; then
+    echo "Must pass output directory"
+    exit 1
+fi
+
+CONTRACTS=("CanonicalTransactionChain")
+PKG=legacy_bindings
+
+for contract in ${CONTRACTS[@]}; do
+    TMPFILE=$(mktemp)
+    npx hardhat inspect $contract bytecode > "$TMPFILE"
+    ABI=$(npx hardhat inspect $contract abi)
+
+    outfile="$OUTDIR/$contract.go"
+
+    echo "$ABI" | abigen --abi - --pkg "$PKG" --bin "$TMPFILE" --type $contract --out "$outfile"
+
+    rm "$TMPFILE"
+done