[pl] Fix xpce test

[Petr Pisar]

commit ae366d8c20ecb1da1ae7ae521df281734e600970
Author: Petr Písař <ppisar at redhat.com>
Date:   Thu Aug 23 17:20:58 2012 +0200

    Fix xpce test

 tests/xpce/Makefile |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/tests/xpce/Makefile b/tests/xpce/Makefile
index 57376fa..50f5468 100644
--- a/tests/xpce/Makefile
+++ b/tests/xpce/Makefile
@@ -1,5 +1,5 @@
-LIBDIR=$(shell readlink $$(type -p swipl) | grep -o lib[^/]*)
-IMAGE=/usr/$(LIBDIR)/swipl-6.0.2/library/pldoc/reload.gif
+PREFIX=$(shell readlink -f $$(type -p swipl) | grep -o '/.*lib[^/]*/[^/]*')
+IMAGE=$(PREFIX)/library/pldoc/reload.gif
 
 all: show.pl $(IMAGE)
 	printf "show('%s').\n" $(IMAGE) | swipl -s show.pl