configure: Link QEMU against 'liburcu-bp'

This library is needed when using 'ust/tracepoint.h'.

Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Lluís Vilanova <vilanova@ac.upc.edu>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
diff --git a/configure b/configure
index c0a542b..319355b 100755
--- a/configure
+++ b/configure
@@ -2672,7 +2672,7 @@
 int main(void) { return 0; }
 EOF
   if compile_prog "" "" ; then
-    LIBS="-lust $LIBS"
+    LIBS="-lust -lurcu-bp $LIBS"
   else
     echo
     echo "Error: Trace backend 'ust' missing libust header files"