$ ./flutter/bin/et build -c host_debug_unopt_arm64 //flutter/impeller:impeller_unittests
[2024-05-15 15:03:50.299682] ERROR: Failed to parse JSON output from `gn desc`:
FormatException: Unexpected character (at character 1)
WARNING at build arg file (use "gn args <out_dir>" to edit):47:24: Build ar...
^

[2024-05-15 15:03:50.306646] ERROR: FatalError caught in main. Please file a bug
error: Failed to parse JSON output from `gn desc`:
FormatException: Unexpected character (at character 1)
WARNING at build arg file (use "gn args <out_dir>" to edit):47:24: Build ar...
^


stack: #0      Logger.fatal (package:engine_tool/src/logger.dart:125:5)
#1      Gn.desc (package:engine_tool/src/gn.dart:69:27)
<asynchronous suspension>
#2      BuildCommand.run (package:engine_tool/src/commands/build_command.dart:85:41)
<asynchronous suspension>
#3      CommandRunner.runCommand (package:args/command_runner.dart:212:13)
<asynchronous suspension>
#4      ToolCommandRunner.run (package:engine_tool/src/commands/command_runner.dart:97:14)
<asynchronous suspension>
#5      main (package:engine_tool/main.dart:86:19)
<asynchronous suspension>