[gn build] Port 00128a20eec2

Author: llvmgnsyncbot

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

@@ -280,6 +280,7 @@ copy("Headers") {
     "rdpruintrin.h",
     "rdseedintrin.h",
     "riscv_bitmanip.h",
+    "riscv_corev_alu.h",
     "riscv_crypto.h",
     "riscv_ntlh.h",
     "rtmintrin.h",