Updated `01_acpi` script.

gistfile1.txt

#! /bin/sh -e

# Uncomment to load custom ACPI table
GRUB_CUSTOM_ACPI="/boot/dsdt.aml"

# DON'T MODIFY ANYTHING BELOW THIS LINE!

prefix=/usr
exec_prefix=${prefix}
libdir=${exec_prefix}/lib

. "$pkgdatadir/grub-mkconfig_lib"

# Load custom ACPI table
if [ x${GRUB_CUSTOM_ACPI} != x ] && [ -f ${GRUB_CUSTOM_ACPI} ] \
        && is_path_readable_by_grub ${GRUB_CUSTOM_ACPI}; then
    echo "Found custom ACPI table: ${GRUB_CUSTOM_ACPI}" >&2
    prepare_grub_to_access_device `${grub_probe} --target=device ${GRUB_CUSTOM_ACPI}` | sed -e "s/^/  /"
    cat << EOF
acpi (\$root)`make_system_path_relative_to_its_root ${GRUB_CUSTOM_ACPI}`
EOF
fi