phpstan: Errors when using parallalism

Testing the new parallel option on circleci, and I’m seeing some errors. It’s notable that phpstan will see 36 cores on circleci runners.

 Internal error: Failed to create directory                    
         "/tmp/phpstan/cache/PHPStan" (mkdir(): File exists).          
         Run PHPStan with --debug option and post the stack trace to:  
         https://github.com/phpstan/phpstan/issues/new 

It seems this isn’t playing nicely for some reason.

Internal error: Could not write data to cache file            
         /tmp/phpstan/cache/PHPStan/p4n9h3psuh.tmp.      
         Run PHPStan with --debug option and post the stack trace to:  
         https://github.com/phpstan/phpstan/issues/new 

--debug seems to disable parallelism, so I can’t really get you more info than that, sorry.