Draft: [soldier] ABI: Add libXNVCtrl.so.0
MangoHUD uses this to get performance metrics from older NVIDIA GPUs. If we include it in the soldier runtime, it'll always be present even if the user does not have it installed on the host system.
Resolves: steam-runtime-tools#82 (closed)
Should also be cherry-picked to sniper and medic, assuming this is successful.