我有一个在flutter中开发的应用程序，我通过Microsoft应用程序中心为android和ios构建了我的应用程序，但是ios构建大多数时候都失败了（构建过程花费了30多分钟，所以失败了），但这是日志，有人可以帮我找出问题所在吗？
顺便说一句。 Android构建始终成功。
2020-02-29T10:54:57.1593575Z ContinueOnError: False
2020-02-29T10:54:57.1593575Z TimeoutInMinutes: 30
2020-02-29T10:54:57.1593575Z CancelTimeoutInMinutes: 0
2020-02-29T10:54:57.1593575Z Expand:
2020-02-29T10:54:57.1593575Z MaxConcurrency: 0
2020-02-29T10:54:57.3543597Z ########## System Pipeline Decorator(s) ##########
2020-02-29T10:54:57.3543597Z Begin evaluating template 'system-pre-steps.yml'
Evaluating: eq('true', variables['system.debugContext'])
Expanded: eq('true', Null)
Result: False
Evaluating: resources['repositories']['self']
Expanded: Null
Result: False
Finished evaluating template 'system-pre-steps.yml'
********************************************************************************
Template and static variable resolution complete. Final runtime YAML document:
steps: []
2020-02-29T10:54:57.3543597Z MaxConcurrency: 0
2020-02-29T10:54:57.3594203Z ##[section]Finishing: Prepare job Phase_1```