Without the swift standard library, what can be done? Doesn't the standard library include all of the basic types, like Array, Int, etc?
Fixed-size integers and UnsafeMutablePointer are supported, so it is basically C with different syntax:
Except it has a stronger type checking and safety.
The solution doesn't involve changing the compiler or building everything into the executable. Instead, this is a makefile coordinated pipeline (front-end swiftc, back-end clang) plus a start.s and a system.c file that omit any need for typical standard library components in the first place.
i.e. a "bare metal" compilation