Environment.swift

public struct Environment {
  init() {
    print("Current.init")
  }

  public var name = "World"
}

public var Current: Environment! = Environment()

Main.swift

import Environment

print("Hello")
print(Current.name)

Makefile

default: compile
	./Main

compile: Main

Main: Environment
	swiftc Main.swift -I . -L . -lEnvironment

Environment: Environment.swift libEnvironment.dylib
	swiftc -emit-library -emit-module -parse-as-library Environment.swift