Fix Linux build issue

Author: Kyle-Ye

Sources/OpenSwiftUI/Util/AnyAttributeFix.swift

@@ -13,6 +13,8 @@ package typealias AttributeType = OpenSwiftUICore.AttributeType
 extension AnyAttribute {
     package static var `nil`: AnyAttribute { AnyAttribute(rawValue: 0x2) }
 
+    package static var currentWasModified: Bool { false }
+
     package var source: AnyAttribute? {
         get { preconditionFailure("#39") }
         nonmutating set { preconditionFailure("#39") }

Sources/OpenSwiftUICore/Util/AnyAttributeFix.swift

@@ -60,6 +60,8 @@ package struct AttributeType {
 extension AnyAttribute {
     package static var `nil`: AnyAttribute { AnyAttribute(rawValue: 0x2) }
 
+    package static var currentWasModified: Bool { false }
+
     package var source: AnyAttribute? {
         get { preconditionFailure("#39") }
         nonmutating set { preconditionFailure("#39") }