op-bindings: add OptimismMintableERC20Factory (#3292)

Was forgotten because it lives in the `universal`
directory and not the `L2` directory

op-bindings/Makefile

@@ -12,7 +12,8 @@ bindings: l1block-bindings \
 	address-manager-bindings \
 	l2-cross-domain-messenger-bindings \
 	l2-standard-bridge-bindings \
-	sequencer-fee-vault-bindings
+	sequencer-fee-vault-bindings \
+	optimism-mintable-erc20-factory-bindings
 
 deployed: l1-block-deployed \
 	optimism-portal-deployed \
@@ -58,6 +59,9 @@ l2-standard-bridge-bindings:
 sequencer-fee-vault-bindings:
 	./gen_bindings.sh contracts/L2/SequencerFeeVault.sol:SequencerFeeVault $(pkg)
 
+optimism-mintable-erc20-factory-bindings:
+	./gen_bindings.sh contracts/universal/OptimismMintableERC20Factory.sol:OptimismMintableERC20Factory $(pkg)
+
 mkdir:
 	mkdir -p bin $(pkg)