Build: Support for cmake or custom build command

[BartolomeyKant]

I'm working with cmake. And usually I configured it the following way

mkdir build
cd build
cmake -GNinja ..

And for building I just call ninja.

I want to configure Build to run ninja on specified directory. It is possible through the call ninja -C /path/to/build or cding to build dir and call ninja without arguments. It is also possible to provide a selected target to ninja's argument ninja lib1 or ninja bin1.

[adamharrison]

Yup; this should be very doable. I'll add in a backend for this. I'm super busy at the moment, but should be able to get this this in hopefully soon.