Factory for use with CompilerCustomizationBuilder. Allows the construction of source aware customizers. Syntax:

    // apply CompileStatic AST annotation on .sgroovy files
    builder.source(extension: 'sgroovy') {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on .sgroovy or .sg files
    builder.source(extensions: ['sgroovy','sg']) {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on .sgroovy or .sg files
    builder.source(extensionValidator: { it.name in ['sgroovy','sg']}) {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on files whose name is 'foo'
    builder.source(basename: 'foo') {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on files whose name is 'foo' or 'bar'
    builder.source(basenames: ['foo', 'bar']) {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on files whose name is 'foo' or 'bar'
    builder.source(basenameValidator: { it in ['foo', 'bar'] }) {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on files that do not contain a class named 'Baz'
    builder.source(unitValidator: { unit -> !unit.AST.classes.any { it.name == 'Baz' } }) {
        ast(CompileStatic)
    }

    // apply CompileStatic AST annotation on class nodes that end with 'CS'
    builder.source(classValidator: { cn -> cn.name.endsWith('CS') }) {
        ast(CompileStatic)
    }