Implement Buck driven build

To build this plugin with Buck, clone it in plugins directory in Gerrit tree
and issue this command from the root of the Gerrit tree:

  buck build plugins/serviceuser:serviceuser

The output is found in:

  buck-out/gen/plugins/serviceuser/serviceuser.jar

Change-Id: I39f27f9fc19c0e96ab9948c6292f5e571ab26d40
diff --git a/BUCK b/BUCK
new file mode 100644
index 0000000..d772eec
--- /dev/null
+++ b/BUCK
@@ -0,0 +1,14 @@
+MODULE = 'com.googlesource.gerrit.plugins.serviceuser.CreateServiceUserForm'
+
+gerrit_plugin(
+  name = 'serviceuser',
+  srcs = glob(['src/main/java/**/*.java']),
+  resources = glob(['src/main/**/*']),
+  gwt_module = MODULE,
+  manifest_entries = [
+    'Gerrit-PluginName: serviceuser',
+    'Gerrit-Module: com.googlesource.gerrit.plugins.serviceuser.Module',
+    'Gerrit-HttpModule: com.googlesource.gerrit.plugins.serviceuser.HttpModule',
+    'Gerrit-SshModule: com.googlesource.gerrit.plugins.serviceuser.SshModule',
+  ],
+)
diff --git a/src/main/resources/Documentation/build.md b/src/main/resources/Documentation/build.md
index f08609f..cc263e9 100644
--- a/src/main/resources/Documentation/build.md
+++ b/src/main/resources/Documentation/build.md
@@ -1,12 +1,34 @@
 Build
 =====
 
-This plugin is built with Maven.
+This plugin is built with Buck.
+Clone or link this plugin to the plugins directory of Gerrit tree
+and issue the command:
+
+```
+  buck build plugins/serviceuser:serviceuser
+```
+
+The output is created in
+
+```
+  buck-out/gen/plugins/serviceuser/serviceuser.jar
+```
+
+This project can be imported into the Eclipse IDE:
+
+```
+  ./tools/eclipse/project.py
+```
+
+Note for compatibility reasons Maven build is provided, but it considered to
+be deprecated and is going to be removed in one of the future versions of this
+plugin.
 
 ```
   mvn clean package
 ```
 
-The plugin build requires the Gerrit Plugin API to be available.
+When building with Maven, the Gerrit Plugin API must be available.
 How to build the Gerrit Plugin API is described in the [Gerrit
 documentation](../../../Documentation/dev-buck.html#_extension_and_plugin_api_jar_files).