From: https://github.com/luceneplusplus/LucenePlusPlus/pull/218

From: Gianfranco Costamagna <locutusofborg@debian.org>
Date: Mon, 8 Sep 2025 15:05:34 +0200
Subject: [PATCH] Find and use system googletest if available

--- a/src/test/CMakeLists.txt
+++ b/src/test/CMakeLists.txt
@@ -8,8 +8,10 @@ if(MSVC)
   set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
 endif()
 
-add_subdirectory(gtest)
-
+find_package(GTest)
+if(NOT GTEST_FOUND)
+  add_subdirectory(gtest)
+endif()
 
 ####################################
 # src