Rebuilt cross-toolchain (clang/gcc/rust installs) following the relibc,
kernel, and base fork changes — stale prefix artifacts are the primary
cause of 'undefined reference' link errors after fork work. Tracked for
disaster recovery per 96e4a29592.
make distclean destroyed prefix/ which was entirely gitignored.
Now prefix/*.tar.gz (clang/gcc/rust toolchain, ~408MB) is tracked.
Recovery after distclean: git checkout + make prefix (extract + build relibc).
prefix/.gitignore allows only *.tar.gz files; extracted directories,
relibc-install, and sysroot remain untracked (regenerable).
vasilito