Check if PHPCS is installed before trying to install a new copy

tests/bin/phpcs.sh

@@ -5,6 +5,11 @@ if [[ ${RUN_PHPCS} == 1 ]]; then
 	IGNORE="tests/cli/,includes/libraries/,includes/api/legacy/"
 
 	if [ "$CHANGED_FILES" != "" ]; then
+		if [ ! -f "./vendor/bin/phpcs" ]; then
+			# Install wpcs globally
+			composer require woocommerce/woocommerce-sniffs
+		fi
+
 		echo "Running Code Sniffer."
 		./vendor/bin/phpcs --ignore=$IGNORE --encoding=utf-8 -s -n -p $CHANGED_FILES
 	fi