[PATCH] amdgpu: add env support for amdgpu.ids path

[PATCH] amdgpu: add env support for amdgpu.ids path

In some cases, like when building a Snap application that uses
libdrm, the `amdgpu.ids` file isn't directly available at the
compiling place, but inside a mounted folder. This forces each
application to link/bind the file from the current place
(usually at the $SNAP/gnome-platform/usr/share/libdrm/amdgpu.ids)
which is cumbersome.

This patch allows to set an environment variable, called
AMDGPU_ASIC_ID_TABLE_PATH, where the file will be also searched
if it isn't located in the default, meson-configured, path.

Gbp-Pq: Name amdgpu-add-env-support-for-amdgpu-ids.patch