This custom loader for .rpx files which can be used with any payload.elf loader. (For example PayloadFromRPX or JsTypeHax)
Place the payload.elf in the sd:/wiiu folder of your sd card and run a exploit which loads payload.elf, this will load the sd:/wiiu/payload.rpx into memory and execute it. The maximum size of the payload.rpx depends on the size of this loader, but should > 7Mib.
For building you just need wut and the ppc-portlibs ((dkp-)pacman -Syu ppc-portlibs) installed, then use the make command.
It's possible to use a docker image for building. This way you don't need anything installed on your host system.
# Build docker image (only needed once)
docker build . -t customrpxloader-builder
# make
docker run -it --rm -v ${PWD}:/project customrpxloader-builder make
# make clean
docker run -it --rm -v ${PWD}:/project customrpxloader-builder make clean
docker run --rm -v ${PWD}:/src wiiuenv/clang-format:13.0.0-2 -r ./src -i