Exposed project id and project directory to build scripts.

lib/build.rb

@@ -143,6 +143,9 @@ module GitlabCi
       @process.environment['CI_BUILD_REF_NAME'] = @ref_name
       @process.environment['CI_BUILD_ID'] = @id
+      @process.environment['CI_PROJECT_ID'] = @project_id
+      @process.environment['CI_PROJECT_DIR'] = project_dir
+
       @process.start
       @tmp_file_path = @tmp_file.path