Release 0.13.0

Release 0.12.0

Merge pull request #731 from Prince213/readme-fix

Readme fix

Update submodule to latest commit (#439)

build_runner: Require some paths to be given (#369)

We now require the following to ge given in the cli args:
- zig_exe
- build_root
- cache_root
- global_cache_root

This fixes the path for packages that use one or more from the above to place
their files.

Better `zig build config`