我尝试将firebase从4.2.0版升级到5.4.1版。我在构建IOS时遇到此错误:Undefinedsymbolsforarchitecturex86_64:"_OBJC_CLASS_$_GULAppEnvironmentUtil",referencedfrom:objc-class-refinFirebaseCoreDiagnostics(FIRDiagnostics_b8d2083bbf595e32a15f4c92bf56379b.o)"_OBJC_CLASS_$_GULNetwork",referencedfrom:objc-class-refinFirebaseCoreDi