Added help to build distributions in docs (#1898)

Signed-off-by: Sarat Vemulapalli <vemulapallisarat@gmail.com>

DEVELOPER_GUIDE.md

@@ -7,6 +7,7 @@
       - [Runtime JDK](#runtime-jdk)
       - [Windows](#windows)
       - [Docker](#docker)
+    - [Build](#build)
     - [Run Tests](#run-tests)
     - [Run OpenSearch](#run-opensearch)
   - [Use an Editor](#use-an-editor)
@@ -82,6 +83,22 @@ Download and install [Docker](https://docs.docker.com/install/), required for bu
 
 On Windows, [use Docker Desktop 3.6](https://docs.docker.com/desktop/windows/release-notes/3.x/). See [OpenSearch#1425](https://github.com/opensearch-project/OpenSearch/issues/1425) for workarounds and issues with Docker Desktop 4.1.1.
 
+### Build
+
+To build all distributions of OpenSearch, run:
+
+```
+./gradlew assemble
+```
+
+To build a distribution to run on your local platform, run:
+
+```
+./gradlew localDistro
+```
+
+All distributions built will be under `distributions/archives`.
+
 ### Run Tests
 
 OpenSearch uses a Gradle wrapper for its build. Run `gradlew` on Unix systems, or `gradlew.bat` on Windows in the root of the repository.