Allow dtest to find files relative to the working directory when invoked via bazel

[tameware]

Right now this works, from the repo root:

bazel-bin/library/tests/dtest -f hands/list1.txt

This does not work:

bazelisk run //library/tests:dtest -- -f hands/list1.txt

Input file 'hands/list1.txt' not found
Also tried hands/listhands/list1.txt.txt under the current directory, BUILD_WORKING_DIRECTORY, BUILD_WORKSPACE_DIRECTORY, and relative to the dtest binary