Samples build.zig cannot be directly used #597
Description
If you try to build a sample directly, it errors:
$ cd samples\minimal_d3d12
$ zig build
...\samples\minimal_d3d12\build.zig:4:25: error: import of file outside module path: '../../build.zig'
const Options = @import("../../build.zig").Options;
^~~~~~~~~~~~~~~~~
I think we can refactor to directly pass in target and optimize but duplicate all other options as b.option.