Bld extension to generate ANTLR4 parsers

A bld extension for generating Java sources from ANTLR4 parsers.

The complete document of Antrl4Operation can be found in its javadocs.

This is an example usage where your ANTLR4 sources would be located at src/main/antlr and the parsers generated into build/generated. The compile command then uses an adapted CompileOperation to include the generated sources into the main source directories.

private final Antlr4Operation antlr4Operation_ = new Antlr4Operation();
@BuildCommand
public void generateGrammar()
throws Exception {
    antlr4Operation_.executeOnce(o -> o
        .sourceDirectories(List.of(new File(srcMainDirectory(), "antlr")))
        .outputDirectory(new File(buildDirectory(), "generated"))
        .visitor()
        .longMessages());
}

// compileOperation_ is part of the main project
public void compile()
throws Exception {
    generateGrammar();
    compileOperation_.executeOnce(o -> o
        .fromProject(this)
        .mainSourceDirectories(List.of(antlr4Operation_.outputDirectory())));
}