Log the executed spawns into this file as length-delimited ExecLogEntry protos, according to src/main/protobuf/spawn.proto. The entire file is zstd compressed. This is an experimental format under active development, and may change at any time. Related flags: --execution_log_binary_file (binary protobuf format; mutually exclusive), --execution_log_json_file (text JSON format; mutually exclusive), --subcommands (for displaying subcommands in terminal output).