Premake is not creating Mac app bundle directory for windowed apps

Hi, I am in the process of upgrading premake in one of my projects and premake5 is no longer creating the Mac app bundle directory structure project.app/Contents/MacOS.

Steps to reproduce:

1. Copy the contents below into simple.lua
2. Run premake5 ./premake5 --file=simple.lua gmake
3. build the project cd build_simple_5 && make
4. The project will be built, but there is no sign of the app bundle files.
5. Repeat steps 1-4, but using the contents of premake4.lua below and
   using a previous version of premake. Notice that the following files are
   created:

I expected that premake5 create the directories. Was this functionality
removed / migrated?

Thanks

wx_window_tutorial.app
wx_window_tutorial.app/Contents
wx_window_tutorial.app/Contents/MacOS
wx_window_tutorial.app/Contents/MacOS/wx_window_tutorial

simple.lua

solution "simple"
    location "build_simple_5"
    configurations { "Debug", "Release" }

    project "wx_window_tutorial"
        language "C++"
        toolset "clang"
        kind "WindowedApp"
        files {
            "main.cpp"
        }

$ ./premake5 --file=simple.lua --version
premake5 (Premake Build Script Generator) 5.0.0-alpha9

premake4.lua

solution "simple"
    location "build_simple_4"
    configurations { "Debug", "Release" }

    project "wx_window_tutorial"
        language "C++"
        kind "WindowedApp"
        files {
            "main.cpp"
        }
        flags {
            "Symbols"
        }

For reference, the premake4 version I last tested:
$ ./premake4 --version
premake4 (Premake Build Script Generator) 4.4-beta5

main.cpp

#include <iostream>

int main() {
  return 0;
}

Reproduce the issue with simple.lua using premake5 alpha9, the gmake action, and the supplied main.cpp, then compare the generated build output with the premake4 result. Trace how the WindowedApp kind is handled for the gmake build; done means the expected wx_window_tutorial.app/Contents/MacOS directory and executable are created.