Add support for GNU/kFreeBSD

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
diff --git a/exec.c b/exec.c
index 076d26b..eb1ee51 100644
--- a/exec.c
+++ b/exec.c
@@ -463,7 +463,7 @@
             exit(1);
         }
     }
-#elif defined(__FreeBSD__) || defined(__DragonFly__)
+#elif defined(__FreeBSD__) || defined(__FreeBSD_kernel__) || defined(__DragonFly__)
     {
         int flags;
         void *addr = NULL;