Do not import CSystem on Darwin

Author: milseman

Sources/System/Platform/Platform.swift renamed to Sources/System/Internals/CInterop.swift

@@ -14,12 +14,13 @@
 @available(*, deprecated, renamed: "CInterop.Mode")
 public typealias CModeT =  CInterop.Mode
 
-import CSystem
 #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
 import Darwin
 #elseif os(Linux) || os(FreeBSD) || os(Android)
+import CSystem
 import Glibc
 #elseif os(Windows)
+import CSystem
 import ucrt
 #else
 #error("Unsupported Platform")

Sources/System/Internals/Constants.swift

@@ -11,12 +11,13 @@
 // they can be used anywhere without imports and without confusion to
 // unavailable local decls.
 
-import CSystem
 #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
 import Darwin
 #elseif os(Linux) || os(FreeBSD) || os(Android)
+import CSystem
 import Glibc
 #elseif os(Windows)
+import CSystem
 import ucrt
 #else
 #error("Unsupported Platform")

Sources/System/Internals/Exports.swift

@@ -7,8 +7,6 @@
  See https://swift.org/LICENSE.txt for license information
 */
 
-import CSystem
-
 // Internal wrappers and typedefs which help reduce #if littering in System's
 // code base.
 
@@ -17,8 +15,10 @@ import CSystem
 #if os(macOS) || os(iOS) || os(watchOS) || os(tvOS)
 import Darwin
 #elseif os(Linux) || os(FreeBSD) || os(Android)
+import CSystem
 import Glibc
 #elseif os(Windows)
+import CSystem
 import ucrt
 #else
 #error("Unsupported Platform")