For anyone interested, you can build an aroma wuhb by using wuhbtool from dev kit pro. I won't go through in detail how to install devkitpro, wut and wut-tools. You can find instructions here.
https://gbatemp.net/threads/super-mario-64-port-wii-u.571682/post-9836677
You'll need the iconTex.tga, bootTvTex.tga & bootDrcTex.tga files from the forwarder channel on this post
https://gbatemp.net/threads/super-mario-64-port-wii-u.571682/post-9173644
You need to run the mingw64 instance of devkitpro otherwise the rpx won't compile correctly for Aroma
1. Copy devkitPro\tools\bin\wuhbtool.exe to your working directory
2. Build SM64ex or SM64-port from aboood40091 wiiu ports, both works.
3. Copy your compiled .rpx file to your working directory and rename it to sm64.rpx
4. Copy the 3 tga files to your working directory
5. Open cmd / powershell to your working directory and run " .\wuhbtool.exe sm64.rpx sm64.wuhb --name="Super Mario 64 Wii U Port" --author=AboodXD --icon=iconTex.tga --tv-image=bootTvTex.tga --drc-image=bootDrcTex.tga ".
6. Copy the outputted sm64.wuhb to your WiiU/Apps Folder
7. Run and enjoy