[Ecls-list] run-program hangs with threads

[Andy Hefner]

When building ECL (current from git, older versions as well) with
threads enabled (on Linux/x86), run-program hangs. If I place the
following form in a file and run it via "ecl -load test.lisp", it
hangs with no output other than ECL's "Loading" message:

(ext:run-program "echo"
                  (list "hello" "world")
                 :input nil :output t :error t)
(format *trace-output* "~&Program ran?~%")

This occurs with the current version from git as well as various
versions I've pulled over the last two months. Oddly, this form works
correctly when I execute it from within SLIME. It seems related to the
duplicating of the file descriptor by passing T for either :output or
:error, and goes away if I supply nil or an existing stream object
instead.