Because stdlib.h is now indirectly included in dlls/msvcp140_atomic_wait/main.c, you will have to change __std_create_threadpool_work to not use the reserved variable name `environ`. (This is why the tests are failing on GitLab.) In CreateThreadpoolWork that variable is called `environment`, which I think would be a good name in __std_create_threadpool_work too.
In my opinion, the variable rename would be best done in a separate commit before annotating the CRT functions.