Allow using external absl and re2.

CMakeLists.txt

@@ -20,6 +20,15 @@ option(BUILD_GMOCK "Builds the googlemock subproject" ON)
 option(INSTALL_GTEST "Enable installation of googletest. (Projects embedding googletest may want to turn this OFF.)" ON)
 option(GTEST_HAS_ABSL "Use Abseil and RE2. Requires Abseil and RE2 to be separately added to the build." OFF)
 
+if(GTEST_HAS_ABSL)
+  if(NOT TARGET absl::base)
+    find_package(absl REQUIRED)
+  endif()
+  if(NOT TARGET re2::re2)
+    find_package(re2 REQUIRED)
+  endif()
+endif()
+
 if(BUILD_GMOCK)
   add_subdirectory( googlemock )
 else()

googletest/cmake/Config.cmake.in

@@ -4,6 +4,10 @@ if (@GTEST_HAS_PTHREAD@)
   set(THREADS_PREFER_PTHREAD_FLAG @THREADS_PREFER_PTHREAD_FLAG@)
   find_dependency(Threads)
 endif()
+if (@GTEST_HAS_ABSL@)
+  find_dependency(absl)
+  find_dependency(re2)
+endif()
 
 include("${CMAKE_CURRENT_LIST_DIR}/@targets_export_name@.cmake")
 check_required_components("@project_name@")