[opus] libopus cross compile for bf537 runtime error releated to "-lopus"

[Timothy B. Terriberry]

David A. Bardsley wrote:
> ALSA lib
> /home/dab/Pantel/svn/blackfin_env/2011r1/main/blackfin-linux-dist/lib/alsa-lib/alsa-lib-1.0.24/src/dlmisc.c:124:(snd_dlsym_verify)
> unable to verify version for symbol _snd_ctl_hw_open

I don't at all claim to have any knowledge of ALSA, and I have no idea 
why linking against libopus triggers this problem, but 
<http://www.openwall.com/lists/sabotage/2014/11/15/6> suggests the cause 
may be that the linker is dropping the symbol versioning marker symbols 
because they are otherwise unreferenced, and that using ALSA version 
1.0.29 or later would avoid this problem (if built with 
--without-versioning). Similarly, 
<https://forums.gentoo.org/viewtopic-t-693166-start-0.html> suggests 
that using version 1.0.14_rc3 or earlier would, too.