执行 pod install 时提示：
[!] Automatically assigning platform iOS with version 9.0 on target Runner because no platform was specified. Please specify a platform for this target in your Podfile. See https://guides.cocoapods.org/syntax/podfile.html#platform.
修改 Podfile
# Uncomment this line to define a global platform for your project
platform :ios, '15.1'
