[U-Boot] Moving GRUB building to Gitlab CI

[Heinrich Schuchardt]

Hello Tom,

as discussed on IRC it would make sense to provide GRUB for testing in
U-Boot via gitlab.denx.de. Building could be executed via Gitlab CI.

These are the build commands that worked for me to build GRUB for RISC-V
64bit on Debian Buster after installing quite a few dependencies:

git clone https://git.savannah.gnu.org/git/grub.git
cd grub
git checkout grub-2.04
./bootstrap
./configure --target=riscv64 --with-platform=efi \
CC=gcc \
TARGET_CC=riscv64-linux-gnu-gcc \
TARGET_OBJCOPY=riscv64-linux-gnu-objcopy \
TARGET_STRIP=riscv64-linux-gnu-strip \
TARGET_NM=riscv64-linux-gnu-nm \
TARGET_RANLIB=riscv64-linux-gnu-ranlib
make
./grub-mkimage -O riscv64-efi -o grubriscv64.efi --prefix= -d \
grub-core cat chain configfile echo efinet ext2 fat halt help linux \
lsefisystab loadenv lvm minicmd normal part_msdos part_gpt reboot \
search search_fs_file search_fs_uuid search_label serial sleep test \
true

grubriscv64.efi is the file that we would have to copy to as grub.efi to
the tftp directory when testing.

Best regards

Heinrich