[opus] How to cross-compile opus-tools?

[Timothy B. Terriberry]

bat guano wrote:
>> Now make V=1 shows a different error.
>> "src/opusrtp.c:53:24: fatal error: sys/socket.h: No such file or directory"
>>
>> Any ideas?
>>
> Hi
>
> It has cross-compiled OK when I used release code.
>  From here ---> downloads.xiph.org/releases/opus/opus-tools-0.1.5.tar.gz

The latest git has added an RTP transmitter utility, which requires 
system socket libraries Windows does not have. Currently there is no 
configuration option to disable it.