feat: set curl download retry to 3 times

[out0fmemory]

Set curl download retry to 3 times, make it work in pool network

[popcornmix]

Does:
sudo CURL_OPTIONS="--retry 3" rpi-update
do what you want? I'm not sure how many people would benefit from this being a default option.

[out0fmemory]

Does:
sudo CURL_OPTIONS="--retry 3" rpi-update
do what you want? I'm not sure how many people would benefit from this being a default option.

I think this being a default option HAS NO BAD effect to all of us, But it is benefit to some people who have a very pool connect to github, just as in China.

[Ruffio]

@popcornmix what is status on this?