[RFC] trace-cmd: add the ability to install libtracecmd

[Josef Bacik <jbacik@fb.com>]

Hello,

I'm trying to build some custom tracing tools on top of trace-cmd but they
aren't really usefull outside of Facebook so I don't want to shove them into the
actual trace-cmd project.  Instead I'd like to be able to just build libtracecmd
and install that as well as the necessary header files and just link my tools
against that.  I'm shit at userspace stuff like this, so I've just hacked
something together that works for me.  I'm mostly hoping somebody will look at
the Makefile horribleness that I came up with and tell me how to do it right (or
better yet do it for me!)  The second patch just cleans up some stuff to make
the shared library more library esque.  Any feedback would be great.  Thanks,

Josef