tests: test CLONE_CLEAR_SIGHAND

Test that CLONE_CLEAR_SIGHAND resets signal handlers to SIG_DFL for the
child process and that CLONE_CLEAR_SIGHAND and CLONE_SIGHAND are
mutually exclusive.

Cc: Florian Weimer <fweimer@redhat.com>
Cc: libc-alpha@sourceware.org
Cc: linux-api@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v1 */
Link: https://lore.kernel.org/r/20191010133518.5420-2-christian.brauner@ubuntu.com

/* v2 */
Link: https://lore.kernel.org/r/20191011102537.27502-2-christian.brauner@ubuntu.com
- Christian Brauner <christian.brauner@ubuntu.com>:
  - remove unused variable
  - reuse variable in child process instead od declaring a new one
  - move check for mutual exclusivity of CLONE_SIGHAND and
    CLONE3_CLEAR_SIGHAND to top of test before setting up signal
    handlers
  - rename variables

/* v3 */
- Christian Brauner <christian.brauner@ubuntu.com>:
  - s/CLONE3_CLEAR_SIGHAND/CLONE_CLEAR_SIGHAND/g
5 files changed