Add newline to each generated bash script in rbe_test.go. am: 79dcf732 am:...

Add newline to each generated bash script in rbe_test.go. am: 79dcf732 am: b3ae4522 am: 30010ea4

Original change: https://android-review.googlesource.com/c/platform/build/soong/+/1384901

Change-Id: I5afe202f6327da156aef20c50861034152ad97e2