SOCK_NONBLOCK on alpha does not match the kernel value as the default value is not used on this architecture. It needs its own version of bits/socket.h. Patch will follow.
Created attachment 4138 [details] Patch to fix the problem
SOCK_CLOEXEC is also affected, new patch will follow
Created attachment 4595 [details] New patch
I have applied a patch for this issue as discussed on libc-ports.