Add prepare_build.sh

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

.gitlab-ci.yml

 before_script:
+  - ./scripts/prepare_build.sh
   - ruby -v
   - which ruby
-  - apt-get install libicu-dev -y
   - gem install bundler --no-ri --no-rdoc
   - bundle install

scripts/prepare_build.sh

+#!/bin/bash
+if [ -f /.dockerinit ]; then
+    apt-get update -qq
+    apt-get install -y -qq libicu-dev cmake
+else
+    export PATH=$HOME/bin:/usr/local/bin:/usr/bin:/bin
+fi
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