Add package for xmllint, used in CI scripts for parsing pom.xml files

Change-Id: I39e06897fc327c0caa753486d0acd2e8464f4808
diff --git a/packer/provision/basebuild.sh b/packer/provision/basebuild.sh
index 8d832a0..18c53bd 100644
--- a/packer/provision/basebuild.sh
+++ b/packer/provision/basebuild.sh
@@ -30,6 +30,7 @@
         enchant \
         git \
         less \
+        libxml2-utils \
         maven \
         nodejs \
         nodejs-legacy \