Similar to the bazel build, gtest is supposed to pass --has_absl_flags to
gtest_help_test if building with abseil support but neglects to.

--- a/googletest/CMakeLists.txt
+++ b/googletest/CMakeLists.txt
@@ -293,7 +293,11 @@
   py_test(googletest-filter-unittest)
 
   cxx_executable(gtest_help_test_ test gtest_main)
+  if(NOT GTEST_HAS_ABSL)
   py_test(gtest_help_test)
+  else()
+  py_test(gtest_help_test --has_absl_flags)
+  endif()
 
   cxx_executable(googletest-list-tests-unittest_ test gtest)
   py_test(googletest-list-tests-unittest)