Use __builtin_trap() to truly crash the program instead of dereferencing
null pointer which may be optimized by the compiler preventing the crash
from occurring

Signed-off-by: Clint George <clintbgeorge@gmail.com>
---

[] Testing:
The diff between before and after of running the kselftest test of the
module shows no regression on system with x86 architecture

Let me know if any more testing is needed to be done


[] Error log:
~/Desktop/kernel-dev/linux-v1/tools/testing/selftests/coredump$ make LLVM=1 W=1
  CC       stackdump_test
coredump_test_helpers.c:59:6: warning: indirection of non-volatile null pointer will be deleted, not trap [-Wnull-dereference]
   59 |         i = *(int *)NULL;
      |             ^~~~~~~~~~~~
coredump_test_helpers.c:59:6: note: consider using __builtin_trap() or qualifying pointer with 'volatile'
1 warning generated.
  CC       coredump_socket_test
coredump_test_helpers.c:59:6: warning: indirection of non-volatile null pointer will be deleted, not trap [-Wnull-dereference]
   59 |         i = *(int *)NULL;
      |             ^~~~~~~~~~~~
coredump_test_helpers.c:59:6: note: consider using __builtin_trap() or qualifying pointer with 'volatile'
1 warning generated.
  CC       coredump_socket_protocol_test
coredump_test_helpers.c:59:6: warning: indirection of non-volatile null pointer will be deleted, not trap [-Wnull-dereference]
   59 |         i = *(int *)NULL;
      |             ^~~~~~~~~~~~
coredump_test_helpers.c:59:6: note: consider using __builtin_trap() or qualifying pointer with 'volatile'
1 warning generated.


 tools/testing/selftests/coredump/coredump_test_helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/coredump/coredump_test_helpers.c b/tools/testing/selftests/coredump/coredump_test_helpers.c
index a6f6d5f2a..5c8adee63 100644
--- a/tools/testing/selftests/coredump/coredump_test_helpers.c
+++ b/tools/testing/selftests/coredump/coredump_test_helpers.c
@@ -56,7 +56,7 @@ void crashing_child(void)
 		pthread_create(&thread, NULL, do_nothing, NULL);
 
 	/* crash on purpose */
-	i = *(int *)NULL;
+	__builtin_trap();
 }
 
 int create_detached_tmpfs(void)
-- 
2.43.0