Merge pull request #774 from wp-cli/add/phpstan #489

Job	Run time
Build Phar	48s
Functional - WP latest on PHP 7.2 with MySQL 8.0	6m 35s
Functional - WP latest on PHP 7.3 with MySQL 8.0	8m 20s
Functional - WP trunk on PHP 7.2 with MySQL 8.0	5m 46s
Functional - WP trunk on PHP 7.2 with MySQL 5.7	5m 41s
Functional - WP latest on PHP 7.4 with MySQL 8.0	5m 23s
Functional - WP trunk on PHP 7.4 with MySQL 8.0	6m 1s
Functional - WP latest on PHP 8.0 with MySQL 8.0	5m 30s
Functional - WP trunk on PHP 8.0 with MySQL 5.6	5m 31s
Functional - WP trunk on PHP 8.0 with MySQL 8.0	5m 49s
Functional - WP trunk on PHP 8.0 with MySQL 5.7	6m 0s
Functional - WP 4.9 on PHP 7.2 with MySQL 5.6	5m 23s
Functional - WP trunk on PHP 7.2 with MySQL 5.6	5m 41s
Deployment	11s
Build RPM package	0s
Build DEB package	0s
	1h 12m 39s

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