tests: Simplify backtrace-dwarf (gcc cleanup-13.c) testcase.

The testcase originally came from GCC which was testing the runtime
unwinder using _Unwind_ForcedUnwind. Since we are using our own external
unwinder we can just abort at the right place and unwind from there.

Signed-off-by: Mark Wielaard <mjw@redhat.com>
2 files changed