work on test prepare script, make the whole thing optional

prepare-tests.sh

@@ -0,0 +1,30 @@
+#!/bin/bash
+
+# This script installs a plugin which is necessary to run OpenKeychain's tests
+# into the local maven repository, then puts a line to include the -Test
+# subproject into settings.gradle
+
+echo "checking jdk runtime.."
+if ! java -version 2>&1 | grep OpenJDK; then
+    echo "tests will only run on openjdk, see readme for details!" >&2
+    return
+fi
+
+tmpdir="$(mktemp -d)"
+(
+  cd "$tmpdir";
+  git clone https://github.com/nenick/gradle-android-test-plugin.git
+  cd gradle-android-test-plugin
+  echo "rootProject.name = 'gradle-android-test-plugin-parent'" > settings.gradle
+  echo "include ':gradle-android-test-plugin'" >> settings.gradle
+  ./gradlew :gradle-android-test-plugin:install
+)
+rm -rf "$tmpdir"
+
+echo -n "ok, adding tests to include list.. "
+if grep OpenKeychain-Test settings.gradle >/dev/null ; then
+    echo " already in."
+else
+    echo "include ':OpenKeychain-Test'" >> settings.gradle
+    echo "ok"
+fi