Fix issue with memory allocations in lisp::serialise

Was to do with sv_make.

lib/sv.c

@@ -60,7 +60,8 @@ sv_t sv_chop(sv_t sv, u64 size)
 
 sv_t sv_concat(arena_t *allocator, sv_t a, sv_t b)
 {
-  sv_t c = sv_make(allocator, a.data, a.size + b.size);
+  sv_t c = sv_make(allocator, NULL, a.size + b.size);
+  memcpy(c.data, a.data, a.size);
   memcpy(c.data + a.size, b.data, b.size);
   return c;
 }