make start code more versatile

* always align the stack to 16. I saw an instance on x86_64 linux where
   it was needed.

 * detect at runtime if being interpreted by a dynamic loader and if so
   avoid clobbering the fs register.
479f259ea4Andrew Kelley committed on 11/25/2020, 2:51:24 AMparenta1fb10b
2 files changedLine totals unavailable