initrd extra-utils build fails: patchelf "missing ELF header" on lvm/dmsetup

Description

Building NixOS for aarch64-linux fails during initrd extra-utils creation because lvm and dmsetup from pkgs.lvm2 are shell script wrappers instead of ELF binaries. The stage-1 builder runs patchelf on all binaries in extra-utils, which fails on these scripts.

Steps to reproduce

1. Build any NixOS configuration for aarch64-linux that uses the traditional (non-systemd) initrd
2. The build fails during the extra-utils.drv derivation

Error message

building '/nix/store/hpm8jllx9094js2y63m5nxcxzsg6pnhg-extra-utils.drv'...
patching /nix/store/plh2x621r67s8g4ma1ql0jss6k1jvmpd-extra-utils/bin/lvm...
patchelf: missing ELF header
patching /nix/store/plh2x621r67s8g4ma1ql0jss6k1jvmpd-extra-utils/bin/dmsetup...
patchelf: missing ELF header
patching /nix/store/plh2x621r67s8g4ma1ql0jss6k1jvmpd-extra-utils/lib/libpam.so.0...
patchelf: missing ELF header

Affected versions

• Broken: cad22e7d996aea55ecab064e84834289143e44a0 (nixos-unstable ~2025-12-30)
• Working: 2fbfb1d73d239d2402a8fe03963e37aab15abe8b

Root cause

In nixos/modules/system/boot/stage-1.nix, LVM tools are copied unconditionally:

copy_bin_and_libs ${getBin pkgs.lvm2}/bin/dmsetup
copy_bin_and_libs ${getBin pkgs.lvm2}/bin/lvm

The builder then runs patchelf on all files without checking if they're actually ELF binaries.

Suggested fix

Either:

1. Check if files are ELF before running patchelf (e.g., check magic bytes)
2. Make LVM inclusion conditional on actual LVM usage
3. Fix lvm2 package to ensure lvm/dmsetup are actual ELF binaries, not script wrappers

Metadata

• Architecture: aarch64-linux
• NixOS version: 26.05 (unstable)

Start with nixos/modules/system/boot/stage-1.nix and reproduce the traditional initrd extra-utils build on aarch64-linux. Trace copy_bin_and_libs and the extra-utils patchelf step; done when lvm, dmsetup, and libpam no longer cause “missing ELF header” failures during the build.