revdep_rebuild: Fix issue where library is a full path

[mackal]

app-editors/neovim-0.10.0 has one of it's libraries referenced by a full path, which seems to be causing it want to rebuild.

On my system scanelf shows: /usr/bin/nvim;nvim;;libluv.so.1,libvterm.so.0,/usr/lib64/lua/5.1/lpeg.so,libmsgpack-c.so.2,libtree-sitter.so.0,libunibilium.so.4,libluajit-5.1.so.2,libm.so.6,libuv.so.1,libc.so.6;ELFCLASS64

In the LibCheck.search() function it was passing "/usr/lib64/lua/5.1/lpeg.so" to LibCheck.check() which searches by basename, which of course isn't going to match.