[llvm] [OMP] Add omp.h in test (PR #215882)

[Kelvin Li via llvm-commits]

https://github.com/kkwli created https://github.com/llvm/llvm-project/pull/215882

`omp_get_ancestor_thread_num` and `omp_get_team_size` are only declared in `omp.h`.

Fix build breakage in https://github.com/llvm/llvm-project/pull/215841#issuecomment-5271979382

>From 6b5686aacb23bf4861d7bffa4b6c2d0def7428b5 Mon Sep 17 00:00:00 2001
From: Kelvin Li <kli at ca.ibm.com>
Date: Wed, 12 Aug 2026 15:57:48 -0400
Subject: [PATCH] [OMP] Add omp.h in test

The omp_get_ancestor_thread_num routine is declared in omp.h.
---
 offload/test/offloading/ompx_bare_multi_dim.cpp | 1 +
 1 file changed, 1 insertion(+)

diff --git a/offload/test/offloading/ompx_bare_multi_dim.cpp b/offload/test/offloading/ompx_bare_multi_dim.cpp
index aa854114f9914..93a7b3604e411 100644
--- a/offload/test/offloading/ompx_bare_multi_dim.cpp
+++ b/offload/test/offloading/ompx_bare_multi_dim.cpp
@@ -4,6 +4,7 @@
 // REQUIRES: gpu
 // clang-format on
 
+#include <omp.h>
 #include <ompx.h>
 
 #include <cassert>