Missing header on Linux/s390

Patch from Jakub Jelen
diff --git a/sandbox-seccomp-filter.c b/sandbox-seccomp-filter.c
index a8d472a..2831e9d 100644
--- a/sandbox-seccomp-filter.c
+++ b/sandbox-seccomp-filter.c
@@ -50,6 +50,9 @@
 #include <elf.h>
 
 #include <asm/unistd.h>
+#ifdef __s390__
+#include <asm/zcrypt.h>
+#endif
 
 #include <errno.h>
 #include <signal.h>