[Libomptarget][NFC] Add missing LLVM header

openmp/libomptarget/plugins/common/elf_common/ELFSymbols.cpp

@@ -1,3 +1,11 @@
+//===-- ELFSymbols.cpp - ELF Symbol look-up functionality -------*- C++ -*-===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
 #include "ELFSymbols.h"
 
 using namespace llvm;