Bump minimum CMake version to fix build with CMake 4
Unbundle gtest
https://bugs.gentoo.org/863050
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -38,7 +38,7 @@
 	  ENDIF()
 	ENDIF()
 ELSE()
-cmake_minimum_required (VERSION 2.8)
+cmake_minimum_required (VERSION 3.5)
 
 if (NOT DEFINED CMAKE_BUILD_TYPE)
     set (CMAKE_BUILD_TYPE Release CACHE STRING "Build type")
@@ -161,8 +161,6 @@
 
 ################# compile tests ################
 
-ADD_SUBDIRECTORY( lib/googletest )
-
 if(COMPILER_SUPPORTS_CXX11)
   ADD_SUBDIRECTORY( tests )
 endif()