* introduce std.atomic.Int
 * add src-self-hosted/test.zig which is tested by the main test suite
   - it fully utilizes the multithreaded async/await event loop so the
     tests should Go Fast
 * `stage2/bin/zig build-obj test.zig` is able to spit out an error if 2 exported
   functions collide
 * ability for `zig test` to accept `--object` and `--assembly`
   arguments
 * std.build: TestStep supports addLibPath and addObjectFile