contracts: fix build script (#642)

* contracts: fix build script

* chore: add changeset

* Update packages/contracts/scripts/build.sh
Co-authored-by: Liam Horne <liam@lihorne.com>

* build: parallel
Co-authored-by: Liam Horne <liam@lihorne.com>

.changeset/two-houses-work.md

+---
+"@eth-optimism/contracts": patch
+---
+
+Updates the `yarn build` command to not error

packages/contracts/scripts/build.sh

-yarn run build:typescript & yarn run build:contracts
-yarn run build:typescript:ovm & yarn run build:contracts:ovm
+#!/bin/bash
+
+set -e
+
+yarn run build:typescript&
+yarn run build:contracts&
+yarn run build:contracts:ovm&
+wait