Fix Linux build compiler crash

Tracked on upstream with swiftlang/swift#71086

Author: Kyle-Ye

Sources/OpenGraph/OGGraph.swift

@@ -6,7 +6,6 @@
 //
 
 import _OpenGraph
-import Foundation
 
 @_silgen_name("OGGraphArchiveJSON")
 @inline(__always)
@@ -21,6 +20,8 @@ public func graphCreate() -> UnsafeRawPointer?
 public func graphCreateShared(_: UnsafeRawPointer?) -> UnsafeRawPointer?
 
 #if canImport(ObjectiveC)
+import Foundation
+
 @_silgen_name("OGGraphDescription")
 @inline(__always)
 public func graphDescription(_ graph: UnsafeRawPointer? = nil, options: NSDictionary) -> UnsafeRawPointer?

Sources/OpenGraph/TODO/Attribute.swift

@@ -2,10 +2,7 @@ import _OpenGraph
 
 @propertyWrapper
 public struct Attribute<Value> {
-    #if canImport(Darwin)
-    // FIXME: Linux compiler will crash here
     var identifier: OGAttribute
-    #endif
 
     public init() {
         fatalError("TODO")