Installs enchant in GCP host machine

Prior to bootstrapping the virtualenv for building packages, we must
ensure that the "enchant" apt package is present, otherwise installaiton
of the pip dependencies will fail.

devops/gce-nested/gce-runner.sh

@@ -51,6 +51,7 @@ function copy_securedrop_repo() {
 
 # Main logic
 copy_securedrop_repo
+ssh_gce "sudo apt-get update && sudo apt-get install -qq enchant"
 ssh_gce "make build-debs-notest"
 
 # The test results should be collected regardless of pass/fail,