st/omx/tizonia: Add --enable-omx-tizonia flag and build files

Allow only bellagio or tizonia to be used at the same time.
Detect tizonia package config file
Generate libomx_mesa.so and install it to libtizcore.pc::pluginsdir
Only compile empty source (target.c) for now.

GSoC Project link: https://summerofcode.withgoogle.com/projects/#4737166321123328

Acked-by: Leo Liu <leo.liu@amd.com>
Reviewed-by: Julien Isorce <julien.isorce@gmail.com>
10 files changed