Bump up buck version

Change-Id: Iaf0a7c12661525741f929fa5d643e485ed33684f
diff --git a/tools/build/onos-buck b/tools/build/onos-buck
index 2e3a149..d78d923 100755
--- a/tools/build/onos-buck
+++ b/tools/build/onos-buck
@@ -5,8 +5,8 @@
 
 set -e
 
-BUCK_URL="http://onlab.vicci.org/onos/third-party/buck-v2017.11.30.01.zip"
-BUCK_SHA="8f8d807f591d72adfab212fd405237a398e2e836"
+BUCK_URL="http://onlab.vicci.org/onos/third-party/buck-v2017.12.21.01.zip"
+BUCK_SHA="a8527763a314e64f6793067c1fedb60ec63d3cbc"
 
 [  "-U" = "$1" ] && shift && FORCE_UPDATE=True