Emit withPlatformString as an availability workaround for open

Author: milseman

Sources/System/FilePath/FilePathString.swift

@@ -32,10 +32,15 @@ extension FilePath {
   /// The pointer passed as an argument to `body` is valid
   /// only during the execution of this method.
   /// Don't try to store the pointer for later use.
+  @_alwaysEmitIntoClient
   public func withPlatformString<Result>(
     _ body: (UnsafePointer<CInterop.PlatformChar>) throws -> Result
   ) rethrows -> Result {
+    #if !os(Windows)
+    try withCString(body)
+    #else
     try _withPlatformString(body)
+    #endif
   }
 }