parseCommand(s) {
    let re = /--([^=]+)(?:=(.+))?/;
    let m = re.exec(s);

    if (m)
      this.setOptionCoerced(m[1], m[2]);
  }
Parses a part of a command line and sets the respective option.
The following patterns are supported.

  --spread, --spread=true
  --spread=parse
  --spread=false
  --arrowFunctions --arrow-functions
  --modules=amd