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>
diff --git a/meson.build b/meson.build
index 9bb1140..6a13e80 100644
--- a/meson.build
+++ b/meson.build
@@ -485,8 +485,15 @@
 with_gallium_omx = _omx != 'disabled'
 gallium_omx = _omx
 dep_omx = []
+dep_omx_other = []
 if gallium_omx == 'bellagio'
   dep_omx = dependency('libomxil-bellagio')
+elif gallium_omx == 'tizonia'
+  dep_omx = dependency('libtizonia', version : '>= 0.10.0')
+  dep_omx_other = [
+    dependency('libtizplatform'),
+    dependency('tizilheaders')
+  ]
 endif
 
 omx_drivers_path = get_option('omx-libs-path')