Is there any way to use builder pattern with java 8?

Description

I am using this for creating a java library.
my config is as follows

{
  "library": "retrofit2",
  "artifactId": "example",
  "invokerPackage": "in.example.api",
  "apiPackage" : "in.example.api",
  "modelPackage" : "in.example.api",
  "groupId": "in.example",
  "scmDeveloperConnection" : "",
  "url" : "",
  "asyncNative" : true,
  "java8" : true,
  "dateLibrary" : "java8"
}

Sadly the code this generates doesnt have builder pattern for the request objects.
https://github.com/OpenAPITools/openapi-generator/pull/5961 I saw this issue where builder pattern support was added. But it seems to only work when I set library to "native" . However that forces me to use java 11.
Is it possible to generate the similar library with builder pattern using java8 and retrofit2 library?

openapi-generator version

5.0.0-beta

OpenAPI declaration file content or url

Command line used for generation

./openapi-geneartor-cli.sh generate -i ./swagger.json -g java -c ./config.json -o ./

Suggest a fix/enhancement

Thanks!

Start by inspecting how the Java generator handles the retrofit2 library, the java8 setting, and builder generation, then compare the behavior described in PR #5961. Reproduce the shown configuration and command, and define completion as generating request objects with builder support while remaining compatible with Java 8 and Retrofit 2.