resolve test directory

File::Spec->tmpdir may return a symlink as well, so
c41c902ca6fd9f8e352267be64d (test in directories provided by Test::Spec)
still didn't fix darwin (in all cases).

The darwin I tested on gave a tmpdir like:
	/var/folders/OJ/OJjGh2I+HBOinZB8Re8QVU+++TI/-Tmp-
but cpantesters machines are still using a symlinked /tmp.

Use Cwd to find the real path name, hopefully fixing all remaining cases.