src: fix escaping of single quotes in task runner

[aduh95]

FWIW here's the error on current main:

  AssertionError [ERR_ASSERTION]: Expected values to be strictly deep-equal:
  + actual - expected
  
    {
  +   code: 1,
  -   code: 0,
      signal: null,
  +   stderr: "/bin/sh: -c: line 0: unexpected EOF while looking for matching `''\n" +
  +     '/bin/sh: -c: line 1: syntax error: unexpected end of file\n',
  +   stdout: ''
  -   stderr: '',
  -   stdout: `["I think therefore I'm"]\n`
    }

Refs: https://hackerone.com/reports/3817602