Make rhboot/shim inside Ubuntu multipass on macOS, targetting OpenCore.efi as bootloader

shim_make.sh

#!/bin/sh
#
# `./shim_make.sh install` within macOS, then `/Users/{macOS-user}/shim_root/shim_make.sh` within multipass

SHIM_ROOT="shim_root"

GREEN='\033[0;32m'
NC='\033[0m' # No Color

if [ "$1" = "install" ] ; then
    # Install multipass, mount target folder and copy this script to it
    echo
    echo "Installing multipass..."
    brew install --cask multipass

    echo ""
    echo "Launching primary..."
    multipass launch -n primary

    echo ""
    echo "Adding and mounting ~/${SHIM_ROOT}..."
    mkdir ~/${SHIM_ROOT}
    multipass mount ~/${SHIM_ROOT} primary:/Users/$(whoami)/${SHIM_ROOT}

    echo ""
    echo "Copying script..."

    sed "s/{macOS-user}/$(whoami)/g" $0 > ~/${SHIM_ROOT}/shim_make.sh
    chmod +x ~/${SHIM_ROOT}/shim_make.sh

    echo ""
    echo "Run ${GREEN}/Users/$(whoami)/${SHIM_ROOT}/shim_make.sh${NC} within multipass..."
    echo ""
    multipass shell
    exit
fi

# Install dependencies and make
echo "Installing dependencies..."
sudo apt-get update
sudo apt install -y gcc make git libelf-dev

echo ""
echo "Cloning shim..."
git clone https://github.com/rhboot/shim.git
cd shim
git submodule update --init

echo ""
echo "Making..."
DEFAULT_LOADER="\\\\\\\\OpenCore.efi" make

echo ""
echo "Installing..."
rm -rf /Users/{macOS-user}/${SHIM_ROOT}/usr
DESTDIR=/Users/{macOS-user}/${SHIM_ROOT} EFIDIR="OC" OSLABEL="OpenCore" make install

echo ""
echo "Exit to macOS then run ${GREEN}cp /Users/{macOS-user}/${SHIM_ROOT}/boot/efi/EFI/OC/* /Volumes/{ESP}/EFI/OC${NC} ..."

exit

## Re-make
make clean
rm -rf /Users/{macOS-user}/${SHIM_ROOT}/usr
make
DESTDIR=/Users/{macOS-user}/${SHIM_ROOT} EFIDIR=OC OSLABEL=OpenCore make install

## To debug shim (e.g. within OVMF) make with
OPTIMIZATIONS="-O0" make
## and set 605dab50-e046-4300-abb6-3dd810dd8b23:SHIM_DEBUG to (UINT8)1 (<data>AQ==</data>) in NVRAM