arrow

ARROW-7880: [CI][R] R sanitizer job is not really working

Closes #6450 from nealrichardson/fix-r-sanitizer and squashes the following commits:

0c953b254 <Neal Richardson> Delete commented code
6af182011 <Neal Richardson> Try setting ARROW_HOME
29a6c850e <Neal Richardson> Try to get r-sanitize job back on track

Authored-by: Neal Richardson <neal.p.richardson@gmail.com>
Signed-off-by: Neal Richardson <neal.p.richardson@gmail.com>