[llvm] [flang-rt] fix missing llvm_gtest target (PR #67936)

[Maksim Levental via llvm-commits]

https://github.com/makslevental created https://github.com/llvm/llvm-project/pull/67936

fixes build fail introduced by https://github.com/llvm/llvm-project/commit/6403287eff71a3d6f6c862346d6ed3f0f000eb70.

>From bb702b0c4c7f9cdcaf2ee1112141c8e9d6883b2a Mon Sep 17 00:00:00 2001
From: max <maksim.levental at gmail.com>
Date: Sun, 1 Oct 2023 17:12:30 -0500
Subject: [PATCH] [flang-rt] fix missing llvm_gtest target

---
 flang-rt/unittests/CMakeLists.txt | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/flang-rt/unittests/CMakeLists.txt b/flang-rt/unittests/CMakeLists.txt
index 2b813c6e16dfaa1..cfd6b4c973e50f7 100644
--- a/flang-rt/unittests/CMakeLists.txt
+++ b/flang-rt/unittests/CMakeLists.txt
@@ -33,8 +33,9 @@ function(add_flang_rt_unittest_offload_properties target)
   endif()
 endfunction()
 
-if(NOT TARGET llvm_gtest)
-  message(FATAL_ERROR "Target llvm_gtest not found.")
+set(UNITTEST_DIR ${LLVM_THIRD_PARTY_DIR}/unittest)
+if (NOT TARGET llvm_gtest)
+  add_subdirectory(${UNITTEST_DIR} third-party/unittest)
 endif()
 
 function(add_flang_rt_unittest test_dirname)