Generate UnicodeData using Gradle

[ericvergnaud]

ANTLR tool maven build relies on com.webguys:string-template-maven-plugin:1.1 plugin to generate org/antlr/v5/unicode/UnicodeData.java.
When switching to Gradle, we could not find an equivalent Gradle plugin so we temporarily opted for a tactical solution i.e. use the UnicodeData.java file generated by a previous maven build.
This is acceptable as a tactical solution because the underlying data (emanating from com.ibm.icu.text.UnicodeSet) rarely changes.
But on the long term we need a solution that generates the file dynamically.

Options that come to mind:

• create a Gradle plugin for string-template
• use MavenExecutor, wrapping the existing maven plugin
• use an alternative templating engine for which a Gradle plugin already exists
• move the code to a custom Gradle task
• ...

[DavidGregory084]

I would be happy to help with this @ericvergnaud.

What would the best approach be? Should I open a PR against your fork to be merged into https://github.com/ericvergnaud/antlr5/tree/build-using-gradle?