unbundle gtest and allow the testsuite to be handled via cmake_comment_add_subdirectory
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -9,19 +9,6 @@ set(CMAKE_POSITION_INDEPENDENT_CODE ON)
 # set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fsanitize=address")
 # set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fsanitize=address")
 
-include(FetchContent)
-FetchContent_Declare(
-    googletest
-    GIT_REPOSITORY https://github.com/google/googletest.git
-    GIT_TAG        v1.17.0
-)
-set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
-FetchContent_MakeAvailable(googletest)
-
-include(CTest)
-include(GoogleTest)
-enable_testing()
-
 add_subdirectory(INCHI-1-SRC/INCHI_EXE/inchi-1/src)
 add_subdirectory(INCHI-1-SRC/INCHI_API/libinchi/src)
 add_subdirectory(INCHI-1-TEST/tests/test_unit)
--- a/INCHI-1-TEST/tests/test_unit/CMakeLists.txt
+++ b/INCHI-1-TEST/tests/test_unit/CMakeLists.txt
@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION 3.21 FATAL_ERROR)

+find_package(GTest REQUIRED)
+include(GoogleTest)
+enable_testing()
+
 set(P_BASE "${CMAKE_SOURCE_DIR}/INCHI-1-SRC/INCHI_BASE/src")
 file(GLOB BASE_SOURCES CONFIGURE_DEPENDS
      "${P_BASE}/*.c"
@@ -13,6 +16,6 @@ file(GLOB TEST_SOURCES CONFIGURE_DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/test_*.cpp
 foreach(test_src ${TEST_SOURCES})
     get_filename_component(test_name "${test_src}" NAME_WE)
     add_executable(${test_name} ${test_src})
-    target_link_libraries(${test_name} PRIVATE gtest_main gmock_main test_dependencies libinchi)
+    target_link_libraries(${test_name} PRIVATE GTest::gtest_main GTest::gmock_main test_dependencies libinchi)
     add_test(NAME ${test_name} COMMAND $<TARGET_FILE:${test_name}>)
 endforeach()