cmocka: Only handle SIGBUS and SIGSYS if the system supports it.

Signed-off-by: Andreas Schneider <asn@cryptomilk.org>
diff --git a/src/cmocka.c b/src/cmocka.c
index 8a7c9e1..56ac54a 100644
--- a/src/cmocka.c
+++ b/src/cmocka.c
@@ -296,8 +296,12 @@
     SIGFPE,
     SIGILL,
     SIGSEGV,
+#ifdef SIGBUS
     SIGBUS,
+#endif
+#ifdef SIGSYS
     SIGSYS,
+#endif
 };
 
 /* Default signal functions that should be restored after a test is complete. */