lvm2 support was broken when lvm2 got
converted to a multiple-output derivation:
https://github.com/NixOS/nixpkgs/pull/93024d3a991d410
The `runtimeDependencies` attribute doesn't specifically
look for a `lib` output, so it uses the main `out` output
which no longer contains the library object files.
Since TSM loads the `libdevmapper.so` library
dynamically (likely with `dlfcn.h` functions),
the breakage couldn't be detected at build time.
The commit at hand simply uses
`getLib` to pick the correct output.
6e157a481a