start: disable building from source on failure (#26)
start: disable building from source on failure (#26)

On default, when installation from bottle fails, homebrew would fall back to build from source.
But due to autoupdate happens at background, we cannot notice this in time and may often lead to unwanted battery drain.

I added an environment variable in the update script to prevent this, and this method is found [here](https://discourse.brew.sh/t/solved-option-to-not-build-from-source/3858)
DomT4/homebrew-autoupdate