Add developer documentation

DEVELOPING.md

@@ -0,0 +1,91 @@
+# Documentation for Developers
+
+This document describes how to set up and develop native-build-tools on your local machine.
+
+## Environment
+
+The project uses Gradle as its build system. At the very minimum, you should set `JAVA_HOME` to a [Gradle-compatible JDK](https://docs.gradle.org/current/userguide/compatibility.html).
+
+Some build tasks require a GraalVM JDK (e.g., tests). You should set `GRAALVM_HOME` to an appropriate GraalVM JDK.
+
+## IDE setup
+
+The native-build-tools repo is set up as a multi-project Gradle project, with the Maven and Gradle plugins declared as subprojects of the root project.
+To set the project up in your IDE (e.g., IntelliJ IDEA), import the root project and the IDE should automatically import the subprojects.
+
+## Building & testing
+
+You can use the various commands in the [Gradle build lifecycle](https://docs.gradle.org/current/userguide/build_lifecycle.html) to build and test the project.
+Some examples (all executed from the root of the repository):
+
+```bash
+# Build all projects
+./gradlew assemble
+
+# Build only the native-gradle-plugin (for example)
+./gradlew :native-gradle-plugin:assemble
+
+# Build and run all tests
+./gradlew build
+```
+
+
+## Debugging plugin(s)
+It is often useful to attach a debugger to the Gradle and Maven plugins during a project build.
+
+For the Gradle plugin, this can be accomplished by passing debugger options to the Gradle daemon via `org.gradle.jvmargs`, for example:
+
+```bash
+JAVA_OPTS="-Dorg.gradle.jvmargs=-agentlib:jdwp=transport=dt_socket,server=y,suspend=y,address=8000" ./gradlew assemble
+```
+
+The Gradle daemon will suspend on start-up, wait for you to attach a debugger, and then remain attached for subsequent Gradle commands.
+
+For the Maven plugin, simply use the `mvnDebug` command in place of the `mvn` command.
+
+## Testing local changes with an existing project
+A common development task is to modify a plugin and then test it with an existing project.
+
+To do this, first modify the project as necessary, and then build and publish the plugins to the local Maven repository:
+```bash
+./gradlew publishToMavenLocal --no-parallel
+```
+
+Next, update the plugin version string in the project build files.
+The version can be found manually by searching for the published artifacts in `~/.m2/repository/org/graalvm/buildtools/native/`, or alternatively by checking the `nativeBuildTools` property [here](gradle/libs.versions.toml).
+
+For Gradle, the change looks like the following.
+You may also need to direct Gradle to use the local Maven repository to resolve the plugin:
+```bash
+# build.gradle
+ plugins {
+     ...
+-    id 'org.graalvm.buildtools.native' version '0.9.25'
++    id 'org.graalvm.buildtools.native' version '0.10.5-SNAPSHOT'
+ }
+
+  repositories {
++    mavenLocal()
+     ...
+ }
+
+# settings.gradle
+pluginManagement {
+  repositories {
++     mavenLocal()
+      ...
+  }
+}
+```
+
+For Maven, simply bump the version and it should try the local repository automatically:
+```bash
+# pom.xml
+-        <native.maven.plugin.version>0.9.25</native.maven.plugin.version>
++        <native.maven.plugin.version>0.10.5-SNAPSHOT</native.maven.plugin.version>
+```
+
+Then, run your build as usual. Gradle should find the plugin in the local repository and use it for the build.
+
+
+

README.md

@@ -7,6 +7,9 @@ Repository which contains build tool plugins for interoperability with [GraalVM
 End-user documentation about the plugins can be found [here](https://graalvm.github.io/native-build-tools/).
 
 ## Contributing
+
+Documentation for common developer tasks can be found [here](DEVELOPING.md).
+
 ### Projects
  * [native-maven-plugin](native-maven-plugin/README.md)
  * [native-gradle-plugin](native-gradle-plugin/README.md)

native-gradle-plugin/README.md

@@ -6,12 +6,14 @@ End-user documentation about the plugins can be found [here](https://graalvm.git
 
 ## Building
 
-This plugin can be built with this command:
+This plugin can be built with this command (from the root directory):
 
 ```bash
-./gradlew publishToMavenLocal --no-parallel
+./gradlew :native-gradle-plugin:publishToMavenLocal --no-parallel
 ```
 
+For more details, see the [Developer documentation](../DEVELOPING.md).
+
 In order to run testing part of this plugin you need to get (or build) corresponding `junit-platform-native` artifact.
 
 *You can also take a look at CI workflow [here](../.github/workflows/test-native-gradle-plugin.yml).*

native-maven-plugin/README.md

@@ -6,10 +6,12 @@ End-user documentation about the plugins can be found [here](https://graalvm.git
 
 ## Building
 
-This plugin follows standard Maven plugin conventions and can be built with this command:
+This plugin can be built with this command (from the root directory):
 
-```shell
-./gradlew publishAllPublicationsToCommonRepository
+```bash
+./gradlew :native-maven-plugin:publishToMavenLocal --no-parallel
 ```
 
+For more details, see the [Developer documentation](../DEVELOPING.md).
+
 *You can also take a look at CI workflow [here](../.github/workflows/test-native-maven-plugin.yml).*