Install z3 for t_ems_solcjs

Author: Leo Alt

.circleci/config.yml

@@ -819,7 +819,7 @@ jobs:
           name: Install test dependencies
           command: |
             apt-get update
-            apt-get install -qqy --no-install-recommends nodejs npm cvc4
+            apt-get install -qqy --no-install-recommends nodejs npm cvc4 z3
       - run:
           name: Test solcjs
           no_output_timeout: 30m