How to make vscode not wait for finishing a preLaunchTask?

This worked for me.

Note all these are required, even though none are important:

• problemMatcher.pattern.regexp
• problemMatcher.pattern.file
• problemMatcher.pattern.location
• problemMatcher.pattern.message
• problemMatcher.background.activeOnStart
• problemMatcher.background.beginsPattern
• problemMatcher.background.endsPattern

{
  // See https://go.microsoft.com/fwlink/?LinkId=733558
  // for the documentation about the tasks.json format
  "version": "2.0.0",
  "tasks": [
    {
      "label": "build-extras",
      "type": "shell",
      "isBackground": true,
      "command": "./script/build-extras",

      // This task is run before some debug tasks.
      // Problem is, it's a watch script, and since it never exits, VSCode
      // complains. All this is needed so VSCode just lets it run.
      "problemMatcher": [
        {
          "pattern": [
            {
              "regexp": ".",
              "file": 1,
              "location": 2,
              "message": 3
            }
          ],
          "background": {
            "activeOnStart": true,
            "beginsPattern": ".",
            "endsPattern": ".",
          }
        }
      ]
    }
  ]
}