wanted: (updated?) crosscompile sd-aarch64 hints

[coderofsalvation]

I'm on x86_64 nixos, trying to generate a rpi image.
Like mentioned in the README.md I've added this to my host configuration.nix:

{
  # Enable binfmt emulation of aarch64-linux.
  boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
}

First attempt:

$ nixos-generate -f iso -c server.nix # works no problems here
$ nixos-generate -f sd-aarch64 -c server.nix
error:
       … while calling the 'derivationStrict' builtin
         at <nix/derivation-internal.nix>:34:12:
           33|
           34|   strict = derivationStrict drvAttrs;
             |            ^
           35|

       … while evaluating derivation 'nixos-sd-image-23.11.7761.4a1e67352334-x86_64-linux.img'
         whose name attribute is located at /nix/store/7v1w7191pad8rz4v9dj7xlfcs2kz2m08-nixos-23.11/nixos/pkgs/stdenv/generic/make-derivation.nix:348:7

       … while evaluating attribute 'buildCommand' of derivation 'nixos-sd-image-23.11.7761.4a1e67352334-x86_64-linux.img'
         at /nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/installer/sd-card/sd-image.nix:1:6380:
       … while evaluating the option `sdImage.populateFirmwareCommands':

       … while evaluating definitions from `/nix/var/nix/profiles/per-user/root/channels/nixos/nixos/modules/installer/sd-card/sd-image-aarch64.nix':

       (stack trace truncated; use '--show-trace' to show the full, detailed trace)

       error: Package ‘uboot-rpi_3_defconfig-2023.07.02’ in /nix/store/7v1w7191pad8rz4v9dj7xlfcs2kz2m08-nixos-23.11/nixos/pkgs/misc/uboot/default.nix:127 is not available on the requested hostPlatform:
         hostPlatform.config = "x86_64-unknown-linux-gnu"
         package.meta.platforms = [
           "aarch64-linux"
         ]
         package.meta.badPlatforms = [ ]
       , refusing to evaluate.

       a) To temporarily allow packages that are unsupported for this system, you can use an environment variable
          for a single invocation of the nix tools.

            $ export NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1

          Note: When using `nix shell`, `nix build`, `nix develop`, etc with a flake,
                then pass `--impure` in order to allow use of environment variables.

       b) For `nixos-rebuild` you can set
         { nixpkgs.config.allowUnsupportedSystem = true; }
       in configuration.nix to override this.

       c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
         { allowUnsupportedSystem = true; }
       to ~/.config/nixpkgs/config.nix.

second attempt

$ NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1 nixos-generate -f sd-aarch64 -c server.nix
these 5 derivations will be built:
  /nix/store/3clskg2h9f75iq79bjji0q2xi49lkpvz-uboot-rpi_3_defconfig-2023.07.02.drv
  /nix/store/8l8z4gxlc9s17wbxd0as4bkdkzjvx18i-uboot-rpi_4_defconfig-2023.07.02.drv
  /nix/store/9xw7inmcyr0bymnigfmzb157h8pvpim8-ext4-fs.img.zst.drv
  /nix/store/nmg6pl0d8zyj6rbgivffafdxw52g914y-raspberrypi-armstubs-unstable-2022-07-11.drv
  /nix/store/8l8c7agbp71zpynsymnydmqjccxqpasb-nixos-sd-image-23.11.7761.4a1e67352334-x86_64-linux.img.drv
building '/nix/store/9xw7inmcyr0bymnigfmzb157h8pvpim8-ext4-fs.img.zst.drv'...
building '/nix/store/nmg6pl0d8zyj6rbgivffafdxw52g914y-raspberrypi-armstubs-unstable-2022-07-11.drv'...
building '/nix/store/3clskg2h9f75iq79bjji0q2xi49lkpvz-uboot-rpi_3_defconfig-2023.07.02.drv'...
building '/nix/store/8l8z4gxlc9s17wbxd0as4bkdkzjvx18i-uboot-rpi_4_defconfig-2023.07.02.drv'...
Running phase: unpackPhase
unpacking source archive /nix/store/pk49zldffnjsg9fh9fd5awq3j8lqcyb7-source
/nix/store/9zmr4jlsifabhmr1asbx2dkydkiqp7dn-extlinux-conf-builder.sh: line 138: cd: /nix/var/nix/profiles: No such file or directory
Preparing store paths for image...
Running phase: unpackPhase
unpacking source archive /nix/store/bvzli4m66fv7s3h9yb3ra37r2fbcrdjw-u-boot-2023.07.02.tar.bz2
Running phase: unpackPhase
unpacking source archive /nix/store/bvzli4m66fv7s3h9yb3ra37r2fbcrdjw-u-boot-2023.07.02.tar.bz2
source root is source
Running phase: patchPhase
Running phase: updateAutotoolsGnuConfigScriptsPhase
Running phase: configurePhase
no configure script, doing nothing
Running phase: buildPhase
build flags: SHELL=/nix/store/yisjp6hkqc1qz8lmgnc0dklx0hgg9w2x-bash-5.2-p15/bin/bash CC8=cc LD8=ld OBJCOPY8=objcopy OBJDUMP8=objdump CC7=cc LD7=ld OBJCOPY7=objcopy OBJDUMP7=objdump
cc -DBCM2710=0 -c armstub.S -o armstub.o
cc1: error: bad value 'armv8-a+crc' for '-march=' switch
cc1: note: valid arguments to '-march=' switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client rocketlake icelake-server cascadelake tigerlake cooperlake sapphirerapids alderlake bonnell atom silvermont slm goldmont goldmont-plus tremont knl knm x86-64 x86-64-v2 x86-64-v3 x86-64-v4 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 znver2 znver3 znver4 btver1 btver2 native
make: *** [Makefile:36: armstub.o] Error 1
error: builder for '/nix/store/nmg6pl0d8zyj6rbgivffafdxw52g914y-raspberrypi-armstubs-unstable-2022-07-11.drv' failed with exit code 2;
       last 10 log lines:
       > Running phase: patchPhase
       > Running phase: updateAutotoolsGnuConfigScriptsPhase
       > Running phase: configurePhase
       > no configure script, doing nothing
       > Running phase: buildPhase
       > build flags: SHELL=/nix/store/yisjp6hkqc1qz8lmgnc0dklx0hgg9w2x-bash-5.2-p15/bin/bash CC8=cc LD8=ld OBJCOPY8=objcopy OBJDUMP8=objdump CC7=cc LD7=ld OBJCOPY7=objcopy OBJDUMP7=objdump
       > cc -DBCM2710=0 -c armstub.S -o armstub.o
       > cc1: error: bad value 'armv8-a+crc' for '-march=' switch
       > cc1: note: valid arguments to '-march=' switch are: nocona core2 nehalem corei7 westmere sandybridge corei7-avx ivybridge core-avx-i haswell core-avx2 broadwell skylake skylake-avx512 cannonlake icelake-client rocketlake icelake-server cascadelake tigerlake cooperlake sapphirerapids alderlake bonnell atom silvermont slm goldmont goldmont-plus tremont knl knm x86-64 x86-64-v2 x86-64-v3 x86-64-v4 eden-x2 nano nano-1000 nano-2000 nano-3000 nano-x2 eden-x4 nano-x4 k8 k8-sse3 opteron opteron-sse3 athlon64 athlon64-sse3 athlon-fx amdfam10 barcelona bdver1 bdver2 bdver3 bdver4 znver1 znver2 znver3 znver4 btver1 btver2 native
       > make: *** [Makefile:36: armstub.o] Error 1
       For full logs, run 'nix log /nix/store/nmg6pl0d8zyj6rbgivffafdxw52g914y-raspberrypi-armstubs-unstable-2022-07-11.drv'.
error (ignored): error: cannot unlink '/tmp/nix-build-uboot-rpi_4_defconfig-2023.07.02.drv-1/build/u-boot-2023.07.02/drivers': Directory not empty
error (ignored): error: cannot unlink '/tmp/nix-build-uboot-rpi_3_defconfig-2023.07.02.drv-1/build/u-boot-2023.07.02/drivers': Directory not empty
error: 1 dependencies of derivation '/nix/store/8l8c7agbp71zpynsymnydmqjccxqpasb-nixos-sd-image-23.11.7761.4a1e67352334-x86_64-linux.img.drv' failed to build