[gui-test] revert pre_tests_in_community.gant back

Revert pre_tests_in_community.gant script back to perform a custom shell script before running Ant tasks. Restored from commit 33f706e8

build/scripts/pre_tests_in_community.gant

@@ -0,0 +1,19 @@
+// Copyright 2000-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+
+includeTargets << new File("tests_in_community.gant")
+includeTool << gant.tools.Execute
+
+/**
+ * Configures environment by running a shell script delegating by system property "gant.prepare.test.script" and than runs an default target
+ * in tests_in_community.gant
+ */
+
+target(prepare: "Prepare tests environment") {
+  def uiScript = System.getProperty("gant.prepare.test.script")
+  echo message: 'Preparing tests environment... '
+  echo message: "  Running shell script \"$uiScript\""
+  execute.shell(uiScript)
+  "default"()
+}
+
+setDefaultTarget(prepare)