fix unittests.

7e6ce1a3c52d8533fed92c143419fedb0c93988a fixed abort() to raise
SIGABRT rather than causing SIGSEGV. However, the unittests were
not updated.

Fix unittests.

Change-Id: I73db194127b9b9e9440358aa94273863765a736b
diff --git a/tests/stack_protector_test.cpp b/tests/stack_protector_test.cpp
index 7946bbc..2ba8a87 100644
--- a/tests/stack_protector_test.cpp
+++ b/tests/stack_protector_test.cpp
@@ -119,7 +119,7 @@
 
 TEST(stack_protector_DeathTest, modify_stack_protector) {
   ::testing::FLAGS_gtest_death_test_style = "threadsafe";
-  ASSERT_EXIT(do_modify_stack_chk_guard(), testing::KilledBySignal(SIGSEGV), "");
+  ASSERT_EXIT(do_modify_stack_chk_guard(), testing::KilledBySignal(SIGABRT), "");
 }
 
 #endif