package: Set LD_LIBRARY_PATH for tests to work against shared library

[Conan-Kudo]

When a shared library is built, we need to have the test suite attempt to
use our newly built shared library. Without this, it fails with unresolved
symbols.

[mlschroe]

Actually the test suite does know how to use the newly built library, that's a cmake feature. So I'm kind of puzzled how you get errors.

[Conan-Kudo]

@mlschroe It did not work until I made that change for my build here: https://build.opensuse.org/package/rdiff/home:Pharaoh_Atem:DNF_SUSE:DNF5/libsolv?linkrev=base&rev=2

[Conan-Kudo]

@mlschroe Note this is only broken on openSUSE, as I don't have this problem on Fedora or Mageia.