Instant Netty startup using SubstrateVM Native Image Generation

This is a variant of https://github.com/cstancu/netty-native-demo where instead of using a GraalVM release the master version of SubstrateVM is used instead. Additionally we are using the native-image maven-plugin to allow image building directly from maven.

Setting up SubstrateVM development

To set up your development environment first perform the steps described in Substrate VM - Quick start. After running

$ mx build

in the substratevm subdirectory you also need to run:

$ mx maven-plugin-install

This will install the native-image maven-plugin into your local maven repository. After running the command you will see something like:

[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.335 s
[INFO] Finished at: 2018-06-28T15:18:43+02:00
[INFO] Final Memory: 40M/1009M
[INFO] ------------------------------------------------------------------------

Use the following plugin snippet to enable native-image building for your maven project:

<plugin>
    <groupId>com.oracle.substratevm</groupId>
    <artifactId>native-image-maven-plugin</artifactId>
    <version>feef79390e56345a15937dae9350898fa1f24299-SNAPSHOT</version>
    <executions>
        <execution>
            <goals>
                <goal>native-image</goal>
            </goals>
            <phase>package</phase>
        </execution>
    </executions>
</plugin>

The only thing left to do is either to replace the ${substratevm.version} occurrences in this project pom or instead just run:

$ mvn -Dsubstratevm.version=feef79390e56345a15937dae9350898fa1f24299-SNAPSHOT package

After running mvn package you will find the netty native-image executable in target/netty-svm-http-server. If you want to test the image please refer to the original README file.