Add Identifier to CMakeLists.txt

Author: plemarquand

Sources/SwiftSyntax/CMakeLists.txt

@@ -15,6 +15,7 @@ add_swift_syntax_library(SwiftSyntax
   CommonAncestor.swift
   Convenience.swift
   CustomTraits.swift
+  Identifier.swift
   MemoryLayout.swift
   MissingNodeInitializers.swift
   SourceEdit.swift