steamrt-container: Create symlinks and mount points for pressure-vessel
pressure-vessel needs some mount points to be able to import the host system's libc and libdrm, and some symlinks to be able to run glibc-related binaries from a host system that doesn't use the interoperable ELF interpreter path. Until now we have been doing this in flatdeb-steam, but if we put it under the control of a package, it's somewhat self-documenting, easier to reason about and easier to test.
/cc @denittis @jpwhiting
As mentioned in !50 (closed).
Edited by Simon McVittie