[I CC just in case the ECL mailing list provides me a better answer]
In polishing the upcoming ECL release I discovered that there are two problems when trying to compile cl-unicode. One is due to a bug in ECL, the other one is due to what I believe an error in CL-UNICODE. More precisely, in build/dump.lisp I find
(with-output-to-source-file (out (make-pathname :name "derived-properties"
:directory '(:relative :up "test"))
As far as I know, :UNSPECIFIC is reserved for values that do not make sense for a filesystem, but in this particular case what happens is that the file does not have a file extension, not that extensions (types) do not exist at all.
The consequence is that this lisp form creates an unprintable pathname (one which cannot be written "readably"), both in ECL and CLISP, and ECL righteously complains that this file can not be opened.
I believe the appropriate line should be ":type nil", which works on SBCL, CLISP and ECL, AFAIK.
Am I wrong?
P.S.: This is cl-unicode 0.1.1 distributed by quicklisp.
Instituto de Física Fundamental, CSIC
c/ Serrano, 113b, Madrid 28006 (Spain)