CMake: add UNIFEX_USE_SYSTEM_GTEST option

Author: topazus

CMakeLists.txt

@@ -15,6 +15,8 @@ include(unifex_options)
 include(unifex_env)
 include(unifex_flags)
 
+option(UNIFEX_USE_SYSTEM_GTEST "Use system GTest dependency" OFF)
+
 # The library target is defined in the source subdirectory
 add_subdirectory(source)
 
@@ -32,12 +34,17 @@ if (PROJECT_IS_TOP_LEVEL)
     endif(UNIFEX_BUILD_EXAMPLES)
     # Tests do use gtest
     if(BUILD_TESTING)
-      include(gtest)
-      target_compile_features(gtest PUBLIC cxx_std_17)
-      target_compile_features(gtest_main PUBLIC cxx_std_17)
-      if (UNIFEX_CXX_COMPILER_CLANGCL)
-        target_compile_options(gtest PRIVATE -Wno-error)
-        target_compile_options(gtest_main PRIVATE -Wno-error)
+      if(UNIFEX_USE_SYSTEM_GTEST)
+        find_package(GTest CONFIG REQUIRED)
+        # find_package(GMock REQUIRED)
+      else()
+        include(gtest)
+        target_compile_features(gtest PUBLIC cxx_std_17)
+        target_compile_features(gtest_main PUBLIC cxx_std_17)
+        if (UNIFEX_CXX_COMPILER_CLANGCL)
+          target_compile_options(gtest PRIVATE -Wno-error)
+          target_compile_options(gtest_main PRIVATE -Wno-error)
+        endif()
       endif()
       add_subdirectory(test)
     endif(BUILD_TESTING)

test/CMakeLists.txt

@@ -8,15 +8,15 @@ foreach(file-path ${test-sources})
     string( REPLACE ".cpp" "" file-path-without-ext ${file-path} )
     get_filename_component(file-name ${file-path-without-ext} NAME)
     add_executable( ${file-name} ${file-path})
-    target_link_libraries(${file-name} PUBLIC unifex gtest_main)
+    target_link_libraries(${file-name} PUBLIC unifex GTest::gtest_main)
     add_test(NAME "test-${file-name}" COMMAND ${file-name})
 endforeach()
 
 if(CXX_MEMORY_RESOURCE_HAVE_PMR)
   target_link_libraries(any_unique_test PUBLIC std::memory_resource)
 endif()
 
-target_link_libraries(any_sender_of_test PUBLIC gmock)
-target_link_libraries(async_manual_reset_event_test PUBLIC gmock)
-target_link_libraries(async_scope_test PUBLIC gmock)
-target_link_libraries(async_scope_v0_test PUBLIC gmock)
+target_link_libraries(any_sender_of_test PUBLIC GTest::gmock_main)
+target_link_libraries(async_manual_reset_event_test PUBLIC GTest::gmock_main)
+target_link_libraries(async_scope_test PUBLIC GTest::gmock_main)
+target_link_libraries(async_scope_v0_test PUBLIC GTest::gmock_main)