build: Exclusively use lib/MULTIARCH/steam-runtime-tools-0 for RPATH
This avoids duplicating the libraries depended on by pressure-vessel in lib/MULTIARCH and lib/MULTIARCH/steam-runtime-tools-0.
Edited by Simon McVittie
This avoids duplicating the libraries depended on by pressure-vessel in lib/MULTIARCH and lib/MULTIARCH/steam-runtime-tools-0.