Move icd.d files to libdir to support multiarch applications.
icd.d files were not in the libdir, so we were missing 32 bits files. Now they are moved to libdir and we make sure to read them from there.
The issue was found when running 32 bit application DX11 applications through DXVK.
Fixes #398 (closed).
Downstream issue https://github.com/flathub/com.valvesoftware.Steam/issues/239