Define and use xen libs in a single place

Signed-off-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

configure

@@ -874,16 +874,17 @@ fi
 # xen probe
 
 if test "$xen" = "yes" ; then
-cat > $TMPC <<EOF
+  xen_libs="-lxenstore -lxenctrl -lxenguest"
+  cat > $TMPC <<EOF
 #include <xenctrl.h>
 #include <xs.h>
 int main(void) { xs_daemon_open(); xc_interface_open(); return 0; }
 EOF
-   if $cc $CFLAGS $ARCH_CFLAGS -c -o $TMPO $TMPC $LDFLAGS -lxenstore -lxenctrl 2> /dev/null > /dev/null ; then
-      :
-   else
-      xen="no"
-   fi
+  if $cc $CFLAGS $ARCH_CFLAGS -c -o $TMPO $TMPC $LDFLAGS $xen_libs 2> /dev/null > /dev/null ; then
+    :
+  else
+    xen="no"
+  fi
 fi
 
 ##########################################
@@ -1691,7 +1692,7 @@ if test "$bluez" = "yes" ; then
   echo "#define CONFIG_BLUEZ 1" >> $config_host_h
 fi
 if test "$xen" = "yes" ; then
-  echo "XEN_LIBS=-lxenstore -lxenctrl -lxenguest" >> $config_host_mak
+  echo "XEN_LIBS=$xen_libs" >> $config_host_mak
 fi
 if test "$aio" = "yes" ; then
   echo "#define CONFIG_AIO 1" >> $config_host_h