Abort on external failures in runner mode instead of keep running.

This mainly affects the unit-test mode behavior when dealing with gtest assertion failures.

This is to prepare for persistent mode, where multiple batches run in a single runner process (inside RunnerMain()).
Aborting after failure input ensures Centipede know which batch contains the failure and triage accordingly.

As a side-effect, change a unit-mode e2e test to switch to a non-failing test because the previous test generates an external failure (gTest EXPECT failure) which would cause the runner to abort without destructing the global environment.

PiperOrigin-RevId: 790977540

e2e_tests/functional_test.cc

diff --git a/e2e_tests/functional_test.cc b/e2e_tests/functional_test.cc
index 80fa06d..2cf56d8 100644
--- a/e2e_tests/functional_test.cc
+++ b/e2e_tests/functional_test.cc
@@ -229,7 +229,7 @@
 }
 
 TEST_F(UnitTestModeTest, GlobalEnvironmentGoesThroughCompleteLifecycle) {
-  auto [status, std_out, std_err] = Run("MySuite.GoogleTestExpect");
+  auto [status, std_out, std_err] = Run("MySuite.GoogleTestNeverFails");
   EXPECT_GT(CountSubstrs(std_err, "<<GlobalEnvironment::GlobalEnvironment()>>"),
             0);
   EXPECT_EQ(

fuzztest/internal/centipede_adaptor.cc

diff --git a/fuzztest/internal/centipede_adaptor.cc b/fuzztest/internal/centipede_adaptor.cc
index 13833ca..3497f2c 100644
--- a/fuzztest/internal/centipede_adaptor.cc
+++ b/fuzztest/internal/centipede_adaptor.cc
@@ -419,14 +419,14 @@
   if (centipede_ret != EXIT_SUCCESS) {
     absl::FPrintF(GetStderr(),
                   "[!] Cannot list crash IDs using Centipede - returning "
-                  "empty results.");
+                  "empty results.\n");
     return {};
   }
   const auto contents = ReadFile(env.list_crash_ids_file);
   if (!contents.has_value()) {
     absl::FPrintF(GetStderr(),
                   "[!] Cannot read the result file from listing crash IDs "
-                  "with Centipede - returning empty results.");
+                  "with Centipede - returning empty results.\n");
     return {};
   }
   if (contents->empty()) {
@@ -466,6 +466,11 @@
         fuzzer_impl_.TryParse({(char*)input.data(), input.size()});
     if (parsed_input.ok()) {
       fuzzer_impl_.RunOneInput({*std::move(parsed_input)});
+      if (runtime_.external_failure_detected()) {
+        absl::FPrintF(GetStderr(),
+                      "[!] External failure detected - aborting.\n");
+        std::abort();
+      }
       return true;
     }
     return false;
@@ -705,7 +710,7 @@
     absl::FPrintF(
         GetStderr(),
         "[!] Encountered error when using Centipede to export the crash "
-        "input.");
+        "input.\n");
     return false;
   }
   CentipedeAdaptorRunnerCallbacks runner_callbacks(&runtime_, &fuzzer_impl_,