Enumerate GLVND GLX ICDs - Alternative solution

This is a second alternative solution to solve the problem of listing GLX ICDs.

The first attempt can be found here https://gitlab.steamos.cloud/steam/steam-runtime-tools/merge_requests/92 and here https://gitlab.collabora.com/vivek/libcapsule/merge_requests/24

Following @smcv suggestion https://gitlab.collabora.com/vivek/libcapsule/merge_requests/24#note_50772 this time I used a temporary directory instead of the new --list option of libcapsule.

/cc @smcv @jpwhiting