Make gnu_debuglink_test compatible with aarch64

Summary:
It turns out that __builtin_trap doesn't produce the right kind of crash on aarch64, eliding the stack trace.

Use abort(3) to crash, which reliably generates a crash that the symbolizer can output.

Reviewed By: Gownta

Differential Revision: D50733603

fbshipit-source-id: 3f244a97ce6d0cbdfe2a4fc9c6f6f9b4cadbe4d4

folly/experimental/symbolizer/test/Crash.cpp

@@ -14,9 +14,10 @@
  * limitations under the License.
  */
 
+#include <cstdlib>
 #include <folly/experimental/symbolizer/SignalHandler.h>
 
 int main() {
   folly::symbolizer::installFatalSignalHandler();
-  __builtin_trap();
+  std::abort();
 }

folly/experimental/symbolizer/test/gnu_debuglink_test.sh

@@ -19,8 +19,8 @@ uuid=$(cat /proc/sys/kernel/random/uuid)
 for sig in 1 2 3 13 15; do eval "trap 'exit $((sig + 128))' $sig"; done
 trap 'rm -f "$crash.debuginfo.$uuid" "$crash.strip.$uuid"' 0
 
-${OBJCOPY} --only-keep-debug "$crash" "$crash.debuginfo.$uuid"
-${OBJCOPY} --strip-debug --add-gnu-debuglink="$crash.debuginfo.$uuid" "$crash" "$crash.strip.$uuid"
+objcopy --only-keep-debug "$crash" "$crash.debuginfo.$uuid"
+objcopy --strip-debug --add-gnu-debuglink="$crash.debuginfo.$uuid" "$crash" "$crash.strip.$uuid"
 
 echo '{"op":"start","test":"gnu_debuglink_test"}';
 start=$(date +%s)