Sometimes some OSs (OS X, Linux, Solaris) report EISDIR when unlinking a file.

scsh/filesys.scm

@@ -17,6 +17,7 @@
     (or (with-errno-handler ; Assume it's a file and try.
 	    ((err data)
 	     ((errno/perm) #f) ; Return #f if directory
+	     ((errno/isdir) #f)
 	     ((errno/noent) #t))
 	    (delete-file fname)
 	    #t)