t/test-lib.sh: resolve symlinks in working directory, for pathname comparisons

t/test-lib.sh: resolve symlinks in working directory, for pathname comparisons

Without this, some tests will fail because they compare command output
of subprocesses (such as git) with $PWD -- but subprocesses have the
physical path as their working directory, whereas $PWD contains the
symlinked path.  This fixes it.

Signed-off-by: Lea Wiemann <redacted>
Signed-off-by: Junio C Hamano <redacted>