Patch Doom and Quake to Buildroot

[ChinYikMing]

Summary by cubic

Add Doom and Quake to the Buildroot image so they compile, install, and run out of the box with bundled shareware assets.

• New Features

  • Added doom_riscv and quake as submodules under tests/system/br_pkgs.
  • Enabled BR2_PACKAGE_DOOM and BR2_PACKAGE_QUAKE in Buildroot config.
  • Extended build-linux-image.sh to auto-create Buildroot packages, cross-compile, and install /usr/bin/doom and /usr/bin/quake. Copies DOOM1.WAD and Quake id1/ assets into /root.
  • Patched Doom Makefile to remove nano.specs and static linking, and renamed output to doom.
  • Generated Quake build via CMake with the rv32emu toolchain.

• Migration

  • Run: git submodule update --init --recursive before building.
  • Ensure network access; the build script downloads DOOM1.WAD and Quake shareware assets automatically.

^{Written for commit 77ff531. Summary will update on new commits.}