Added binary check to Makefile

Makefile

@@ -139,6 +139,7 @@ BINARY=$(CURDIR)/build/gaiad
 remotenet-start:
 	@if [ -z "$(DO_API_TOKEN)" ]; then echo "DO_API_TOKEN environment variable not set." ; false ; fi
 	@if ! [ -f $(HOME)/.ssh/id_rsa.pub ]; then ssh-keygen ; fi
+	@if [ -z "`file $(BINARY) | grep 'ELF 64-bit'`" ]; then echo "Please build a linux binary using 'make build-linux'." ; false ; fi
 	cd networks/remote/terraform && terraform init && terraform apply -var DO_API_TOKEN="$(DO_API_TOKEN)" -var SSH_PUBLIC_FILE="$(HOME)/.ssh/id_rsa.pub" -var SSH_PRIVATE_FILE="$(HOME)/.ssh/id_rsa" -var TESTNET_NAME="$(TESTNET_NAME)" -var SERVERS="$(SERVERS)"
 	cd networks/remote/ansible && ANSIBLE_HOST_KEY_CHECKING=False ansible-playbook -i inventory/digital_ocean.py -l "$(TESTNET_NAME)" -e BINARY=$(BINARY) -e TESTNET_NAME="$(TESTNET_NAME)" setup-validators.yml
 	cd networks/remote/ansible && ansible-playbook -i inventory/digital_ocean.py -l "$(TESTNET_NAME)" start.yml