io.standard-paths.unix: use $USER's configured shell.

Hope that '-l -c "echo $PATH"' works.

basis/io/standard-paths/unix/unix.factor

@@ -1,9 +1,9 @@
 ! Copyright (C) 2011 Doug Coleman.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: environment fry io io.encodings.binary
+USING: accessors ascii environment fry io io.encodings.binary
 io.encodings.string io.encodings.utf8 io.files io.launcher
 io.pathnames io.standard-paths kernel math sequences splitting
-system ;
+system unix.users ;
 IN: io.standard-paths.unix
 
 M: unix find-in-path*
@@ -13,10 +13,11 @@ M: unix find-in-path*
 ! iterm2 spews some terminal info on every bash command.
 : parse-login-paths ( seq -- strings )
     dup [ 7 = ] find-last drop [ 1 + tail-slice ] when*
-    utf8 decode ":" split ;
+    utf8 decode [ blank? ] trim ":" split ;
 
 : standard-login-paths ( -- strings )
-    { "bash" "-l" "-c" "echo $PATH" }
+    { "-l" "-c" "echo $PATH" }
+    effective-user-id user-passwd shell>> prefix
     binary <process-reader> stream-contents parse-login-paths ;
 
 M: unix find-in-standard-login-path*