Currently the script xinitrc (placed to /etc/xdg/xfce4/xinitrc in ArchLinux) called by startxfce4 depends in which(1). However, the script has #!/bin/sh shebang, i.e. it's a POSIX sh script, which means that we can use the "command" builtin. This has an advantage of reducing calls to external binaries and remving which(1) dependency. Please consider this replacement, e.g. as in the attached patch.
Created attachment 7730
Patch to replace which(1) with "command" in xinitrc.in.in
*** This bug has been marked as a duplicate of bug 14399 ***