tests: skip tests if strace is not functional

Chances are that strace is available but not functional due to
restricted permissions:

strace: test_ptrace_get_syscall_info: PTRACE_TRACEME: Operation not permitted
strace: ptrace(PTRACE_TRACEME, ...): Operation not permitted
+++ exited with 1 +++

Just skip the tests then.

Signed-off-by: Christian Hesse <mail@eworm.de>
1 file changed