Add newline to each generated bash script in rbe_test.go. am: 79dcf732cc am: b3ae45225e am: 30010ea43f am: 7757aa3778

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

Change-Id: I2e3f2269e8da65388c5d18a602a9fdfe09041738