Add license headers.

Author: jtstogel

libc/src/sys/mman/linux/generic/pkey_common.h

@@ -1,3 +1,11 @@
+//===---------- Generic stub implementations for pkey functionality. ------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
 #ifndef LLVM_SYS_MMAN_LINUX_GENERIC_PKEY_COMMON_H_
 #define LLVM_SYS_MMAN_LINUX_GENERIC_PKEY_COMMON_H_
 

libc/src/sys/mman/linux/x86_64/pkey_common.h

@@ -1,3 +1,11 @@
+//===---------- x86_64-specific implementations for pkey_{get,set}. -------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
 #ifndef LLVM_SYS_MMAN_LINUX_X86_64_PKEY_COMMON_H_
 #define LLVM_SYS_MMAN_LINUX_X86_64_PKEY_COMMON_H_