egl: put full path to libEGL_mesa.so in GLVND json
This is useful when installing to a non-standard path.
glvnd_icd.py
copied & adapted from src/intel/vulkan/anv_icd.py
This is useful when installing to a non-standard path.
glvnd_icd.py
copied & adapted from src/intel/vulkan/anv_icd.py