Blender Git Loki

Install_deps: update to new exr/oiio versions, and (hopefully) fix ILMBase mess

Root of the issue is an (hidden!) parameter in ILMBase cmake options, that
is enabled by default, and force the generation of those ugly lib names
(Imf_2_2.so & co). Why why why enable such thing by default?

Anyway, it should be simpler to build again even on linuxes having the openexr -dev
package installed.

Also, cleaned up a bit things, now we can switch between repo and plain release archive
building from a single place for each lib, instead of commentting/uncommenting everything
each time (for libs where we have some git repo set up for some reason).