[Clang][libc] Add wrapper headers for assert.h for the GPU libc

Summary:
This patch adds the `assert.h` wrapper header. I forgot to include this
in the last patch.

clang/lib/Headers/CMakeLists.txt

@@ -318,11 +318,13 @@ set(openmp_wrapper_files
 )
 
 set(llvm_libc_wrapper_files
+  llvm_libc_wrappers/assert.h
   llvm_libc_wrappers/stdio.h
   llvm_libc_wrappers/stdlib.h
   llvm_libc_wrappers/string.h
   llvm_libc_wrappers/ctype.h
   llvm_libc_wrappers/inttypes.h
+  llvm_libc_wrappers/time.h
 )
 
 include(GetClangResourceDir)

clang/lib/Headers/llvm_libc_wrappers/assert.h

@@ -0,0 +1,34 @@
+//===-- Wrapper for C standard assert.h declarations on the GPU ------------===//
+//
+// 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 __CLANG_LLVM_LIBC_WRAPPERS_ASSERT_H__
+#define __CLANG_LLVM_LIBC_WRAPPERS_ASSERT_H__
+
+#if !defined(_OPENMP) && !defined(__HIP__) && !defined(__CUDA__)
+#error "This file is for GPU offloading compilation only"
+#endif
+
+#include_next <assert.h>
+
+#if __has_include(<llvm-libc-decls/assert.h>)
+
+#if defined(__HIP__) || defined(__CUDA__)
+#define __LIBC_ATTRS __attribute__((device))
+#endif
+
+#pragma omp begin declare target
+
+#include <llvm-libc-decls/assert.h>
+
+#pragma omp end declare target
+
+#undef __LIBC_ATTRS
+
+#endif
+
+#endif // __CLANG_LLVM_LIBC_WRAPPERS_ASSERT_H__