For a cheap, lightweight development laptop I use a Toshiba Chromebook 2 (2015) with a 240GB SSD fitted. Build quality is not up to Apple standards but is still decent.

Screen is much, much better than Macbook Air screen though. Battery life is very good. I use Arch Linux and With a bit of tweaking, everything works (bluetooth, wifi, keyboard backlight, suspend/resume etc).

I can also dual boot into ChromeOS which is quite nice in it's own right. Lovely machine for the money ...