The GCC Atomic Builtins mentioned in the article are not specific to Unix. They are compiler constructs, and depend on specific architecture hardware support. All x86 CPUs have such support for some years now. So these atomic operations can also be used in non-Unix software running on x86 CPUs.
The GCC documentation lists other non-intel architectures which also have the features required to support the atomic built-ins.
The GCC documentation lists other non-intel architectures which also have the features required to support the atomic built-ins.