tasks.json

{
  "version": "2.0.0",
  "tasks": [
    {
      "label": "myPreBuildTask",
      "type": "shell",
      "command": "echo",
      "args": ["${input:myDynamicParameter}"],
      "problemMatcher": []
    }
  ],
  "inputs": [
    {
      "id": "myDynamicParameter",
      "type": "command",
      // first try to read from the disk or select again
      "command": "dynamic-inputs.read",
      "args": {
        "command": "bash",
        // a script which prints JSON array to stdout as the last line
        "args": ["${workspaceFolder}/populate.sh"],
        // memoize the selection for the future
        "var": "myDynamicParameter",
        // map options to values
        "unwrap": "$[*].value",
        "serializer": "plain",
        "quickPickOptions": {
          "canPickMany": true,
          "ignoreFocusOut": true,
          "placeHolder": "Please select an option",
          "title": "Parameter"
        }
      }
    }
  ]
}