Add support for JDK 9,

[soboko]

i.e. don't use tools.jar which doesn't exist any more.

[muffl0n]

I would vote for using SystemUtils.isJavaVersionAtLeast instead of using custom string parsing.

[soboko]

Good point, I've made that change

[ChristianMurphy]

Hey there! 👋

Thanks for opening a pull request with jspc-maven-plugin. 👍 🙇‍♂️
At the moment, the jspc maven plugin does not have an active maintainer to process your request. ⛔
While the Jasig jspc maven plugin is without an active maintainer, we recommend the Apache Sling jspc maven plugin and the Jetty jspc maven plugin as alternatives that are actively maintained. ✅
If you are interested in becoming a project maintainer, there is a uPortal-dev list post where you can register your interest. 📧

Thanks again for contributing to the jspc-maven-plugin! ✨