build failure, clock_gettime undefined, linking libavmedialo.so

[Terrence Enger]

Zolnai,

My build of commit 48eccfb, fetched around 2014-05-16 00:57 UTC, is
failing with messages:

    [build LNK] Library/libavmedialo.so
    /home/terry/lo_hacking/git/libo2/workdir/LinkTarget/StaticLibrary/libcollada2gltf.a(GLTF-Open3DGC.o): In function `o3dgc::Timer::Tic()':
    /home/terry/lo_hacking/git/libo2/workdir/UnpackedTarball/collada2gltf/dependencies/o3dgc/src/o3dgc_common_lib/inc/o3dgcTimer.h:115: undefined reference to `clock_gettime'
    /home/terry/lo_hacking/git/libo2/workdir/LinkTarget/StaticLibrary/libcollada2gltf.a(GLTF-Open3DGC.o): In function `o3dgc::Timer::Toc()':
    /home/terry/lo_hacking/git/libo2/workdir/UnpackedTarball/collada2gltf/dependencies/o3dgc/src/o3dgc_common_lib/inc/o3dgcTimer.h:119: undefined reference to `clock_gettime'

I notice that the files downloaded by `make fetch` were:

    collada2gltf-master-6258611a6a.tar.bz2
    libpng-1.5.18.tar.gz
    OpenCOLLADA-master-6509aa13af.tar.bz2

If I am reading things correctly, the first of these was introduced
by:

    commit d575917016f65a7322817a8e13ec25c52d18a600
    Author: Zolnai Tamás <tamas.zolnai at collabora.com>
    Date:   Thu Apr 10 13:37:38 2014 +0200

        Introduce Collada2gltf external library
    
        Change-Id: I157f175ee6ea719e98ba45133f53cb4d2c3045bb


Suggestions welcome.

Thanks,
Terry.