A simple program that will, given one zig file as input, output a semantically equivalent file
that contains all the code of that file, and the code of the files that file imports. The exceptions
here is std, root and builtin (and anything added with --pkg-begin but that has just not
been implemented).
Right now, this only works for files you would run zig test or zig build-obj on.
zig build-exe doesn't work as I've not thought of a way this generated file can export main
with the way it is generated.