[meta-intel] Supporting multiple GL providers

[Ash Charles]

Hi

I was looking at the meta-intel layer for a good example of how to
support a platform that can use either mesa or a proprietary hardware
accelerated provider for virtual/libgles1, and virtual/libgles2,
virtual/egl.  In the process, I stumbled across
classes/emgd-gl.bbclass.  If I understand commit
49f495e388d986e568f6197075a56a6e7674b2f5 that introduces this class,
all packages that depend on gl will get put in a different package
directory (i.e. a different feed) based on the provider of the GL
library.  This seems like generally useful feature any time there are
multiple GL providers for the same arch---is this assessment
reasonable?

--Ash