Relax dependency on googletest and allow customization of cctz target

CMakeLists.txt

@@ -58,17 +58,21 @@ list(APPEND ABSL_COMMON_INCLUDE_DIRS ${CMAKE_CURRENT_SOURCE_DIR})
 set(CMAKE_CXX_FLAGS "${ABSL_STD_CXX_FLAG} ${CMAKE_CXX_FLAGS}")
 set(CMAKE_CXX_FLAGS "${CMAKE_CXX_WARNING_VLA} ${CMAKE_CXX_FLAGS} ")
 
-
 # find dependencies
 ## pthread
 find_package(Threads REQUIRED)
 
+if(NOT CCTZ_TARGET)
+  set(CCTZ_TARGET cctz)
+endif()
+
 # commented: used only for standalone test
 #add_subdirectory(cctz)
 #add_subdirectory(googletest)
+check_target({${CCTZ_TARGET})
 
 ## check targets
-check_target(cctz)
+if(BUILD_TESTING)
   check_target(gtest)
   check_target(gtest_main)
   check_target(gmock)
@@ -82,5 +86,6 @@ list(APPEND ABSL_TEST_COMMON_LIBRARIES
     gmock
     ${CMAKE_THREAD_LIBS_INIT}
   )
+endif()
 
 add_subdirectory(absl)

absl/time/CMakeLists.txt

@@ -32,7 +32,7 @@ list(APPEND TIME_SRC
   ${TIME_PUBLIC_HEADERS}
   ${TIME_INTERNAL_HEADERS}
 )
-set(TIME_PUBLIC_LIBRARIES absl::base absl::stacktrace absl::int128 cctz)
+set(TIME_PUBLIC_LIBRARIES absl::base absl::stacktrace absl::int128 {CCTZ_TARGET})
 
 absl_library(
   TARGET