seccomp: on s390 the clone() parameters are reversed

Add a bit of code that tries to get the right parameter order in place
for some of the better known architectures, and skips
restrict_namespaces for other archs.

This also bypasses the test on archs where we don't know the right
order.

In this case I didn't bother with testing the case where no filter is
applied, since that is hopefully just an issue for now, as there's
nothing stopping us from supporting more archs, we just need to know
which order is right.

Fixes: #5241

src/basic/raw-clone.h

@@ -47,8 +47,8 @@
 static inline int raw_clone(unsigned long flags) {
         assert((flags & (CLONE_VM|CLONE_PARENT_SETTID|CLONE_CHILD_SETTID|
                          CLONE_CHILD_CLEARTID|CLONE_SETTLS)) == 0);
-#if defined(__s390__) || defined(__CRIS__)
-        /* On s390 and cris the order of the first and second arguments
+#if defined(__s390x__) || defined(__s390__) || defined(__CRIS__)
+        /* On s390/s390x and cris the order of the first and second arguments
          * of the raw clone() system call is reversed. */
         return (int) syscall(__NR_clone, NULL, flags);
 #elif defined(__sparc__) && defined(__arch64__)