original_working_dir is needed even when death tests are disabled

UnitTest::GetInstance()->original_working_dir() is documented public API:
https://github.com/google/googletest/blob/main/docs/reference/testing.md#original_working_dir-unittestoriginal_working_dir

and is used for things like UnitTestOptions::GetAbsolutePathToOutputFile.
So stubbing it to just return an empty string breaks many other unit tests
unnecessarily if you have a filesystem but not death tests

If there's a need to do something special for diskless systems,
seems like they should have a distinct check.

reverts e5686bb
google#3090

googletest/src/gtest-internal-inl.h

@@ -675,7 +675,6 @@ class GTEST_API_ UnitTestImpl {
   void AddTestInfo(internal::SetUpTestSuiteFunc set_up_tc,
                    internal::TearDownTestSuiteFunc tear_down_tc,
                    TestInfo* test_info) {
-#if GTEST_HAS_DEATH_TEST
     // In order to support thread-safe death tests, we need to
     // remember the original working directory when the test program
     // was first invoked.  We cannot do this in RUN_ALL_TESTS(), as
@@ -688,7 +687,6 @@ class GTEST_API_ UnitTestImpl {
       GTEST_CHECK_(!original_working_dir_.IsEmpty())
           << "Failed to get the current working directory.";
     }
-#endif  // GTEST_HAS_DEATH_TEST
 
     GetTestSuite(test_info->test_suite_name(), test_info->type_param(),
                  set_up_tc, tear_down_tc)