ASL is deprecated and replaced by os_log() on iOS. As of iOS 10.3,
calling this function breaks our logging altogether. os_log isn't
available pre-iOS 10.0. Rather than implement version checks and
conditional logic, this change eliminates the existing redirection
altogether. All engine code should be logging via the syslog redirection
implemented in Logger_PrintString in dart_runtime_hooks.cc.
Since stdio redirection is eliminated, we eliminate the flag that
controls whether such redirection is enabled.
2937f06a15