fixed stupid bug #70738 found by alfons hoogervorst

* configure.in: fixed stupid bug #70738 found by alfons hoogervorst
diff --git a/configure.in b/configure.in
index f592392..3c6af23 100644
--- a/configure.in
+++ b/configure.in
@@ -223,7 +223,7 @@
 		if test -r /usr/include/python$PYTHON_VERSION/Python.h
 		then
 		    PYTHON_INCLUDES=/usr/include/python$PYTHON_VERSION
-		    PYTHON_SITE_PACKAGES='$(prefix)/lib/python$PYTHON_VERSION/site-packages'
+		    PYTHON_SITE_PACKAGES='$(prefix)/lib/python$(PYTHON_VERSION)/site-packages'
 		else
 		    echo could not find python$PYTHON_VERSION/Python.h
 		fi