Build gem5 through buildroot

Oh, btw, also make it work, since the build was completely broken since
the recent -K refactoring :0)

build-gem5

@@ -1,37 +0,0 @@
-#/usr/bin/env bash
-set -eu
-arch=x86_64
-while getopts 'a:' OPT; do
-  case "$OPT" in
-    a)
-      arch="$OPTARG"
-      ;;
-  esac
-done
-shift "$(($OPTIND - 1))"
-top="$(pwd)/gem5"
-system_dir="${top}/gem5-system"
-binaries_dir="${system_dir}/binaries"
-disks_dir="${system_dir}/disks"
-mkdir -p "$binaries_dir" "$disks_dir"
-cd "${top}/gem5"
-if [ "$arch" = x86_64 ]; then
-  CC=gcc-6 CXX=g++-6 scons -j"$(nproc)" --ignore-style build/X86/gem5.opt
-  f="${disks_dir}/linux-bigswap2.img"
-  dd if=/dev/zero of="$f" bs=1024 count=65536
-  mkswap "$f"
-  # This file must always be present, despite --kernel overriding that default and selecting the kernel.
-  # I'm not even joking. No one has ever built x86 gem5 without the magic dist dir present.
-  touch "${binaries_dir}/x86_64-vmlinux-2.6.22.9"
-elif [ "$arch" = arm ] || [ "$arch" = aarch64 ]; then
-  # Compilation fails with gcc 7 on that commit.
-  # There were some recent portability patches, so it will likely get there soon.
-  CC=gcc-6 CXX=g++-6 scons -j"$(nproc)" --ignore-style build/ARM/gem5.opt
-  make -C system/arm/dt
-  make -C system/arm/simple_bootloader
-  make -C system/arm/aarch64_bootloader/
-  cp ./system/arm/simple_bootloader/boot_emm.arm "$binaries_dir"
-  cp ./system/arm/aarch64_bootloader/boot_emm.arm64 "$binaries_dir"
-fi
-# TODO vs telnet?
-make -C util/term