adding missing clang dependency for plv8

inian · inian · commit 9ab3573089b0 · 2020-11-11T16:45:09.000+08:00
It is mentioned as one of the dependencies [here](https://plv8.github.io/#building-for-macos-linux).
diff --git a/ansible/tasks/setup-extensions.yml b/ansible/tasks/setup-extensions.yml
@@ -249,6 +249,7 @@
       - libc++1
       - libtinfo5
       - libc++abi1
+      - clang
     update_cache: yes
     install_recommends: no
 
