Build and install gpt-manipulator within build dir
Previously gpt-manipulator was build in external/ directory which casues issues when using on e.g. CI server becasue of changes made by root user. Move build of gpt-manipulator to local build dir.
Previously gpt-manipulator was build in external/ directory which casues issues when using on e.g. CI server becasue of changes made by root user. Move build of gpt-manipulator to local build dir.