lld/test/COFF/relative_search_paths.test

We should be able to find libraries with relative search paths.
# RUN: mkdir -p %t.dir/relative/path
# RUN: cp %p/Inputs/std64.lib %t.dir/relative/path
# RUN: lld-link %p/Inputs/hello64.obj /libpath:%t.dir relative/path/std64.lib /entry:main