[gn build] Port 0481f04

Author: llvmgnsyncbot

llvm/utils/gn/secondary/clang/lib/Headers/BUILD.gn

@@ -256,6 +256,7 @@ copy("Headers") {
     "ppc_wrappers/xmmintrin.h",
     "prfchiintrin.h",
     "prfchwintrin.h",
+    "ptrauth.h",
     "ptwriteintrin.h",
     "raointintrin.h",
     "rdpruintrin.h",