Checking gcc source tree for case of WORDS_BIG_ENDIAN != FLOAT_WORDS_BIG_ENDIAN git grep -P '#define (FLOAT_)?WORDS_BIG_ENDIAN' https://bpa.st/raw/NKQQ I think I only see pdp11:

gcc/config/pdp11/pdp11.h:#define WORDS_BIG_ENDIAN 1
gcc/config/pdp11/pdp11.h:#define FLOAT_WORDS_BIG_ENDIAN 0

qttranslations> -- Install configuration: "Release"
qttranslations> -- Installing: /nix/store/fx4yvhdpq7kld3gq0dqcxd5y7yb4i942-qttranslations-6.9.0/translations/assistant_ar.qm
qttranslations> CMake Error at src/translations/cmake_install.cmake:54 (file):
qttranslations>   file INSTALL cannot copy file
qttranslations>   "/build/qttranslations-everywhere-src-6.9.0/build//nix/store/fx4yvhdpq7kld3gq0dqcxd5y7yb4i942-qttranslations-6.9.0/translations/assistant_ar.qm"
qttranslations>   to
qttranslations>   "/nix/store/fx4yvhdpq7kld3gq0dqcxd5y7yb4i942-qttranslations-6.9.0/translations/assistant_ar.qm":
qttranslations>   Permission denied.
qttranslations> Call Stack (most recent call first):
qttranslations>   src/cmake_install.cmake:47 (include)
qttranslations>   cmake_install.cmake:47 (include)
qttranslations>
qttranslations>
qttranslations> FAILED: CMakeFiles/install.util
qttranslations> cd /build/qttranslations-everywhere-src-6.9.0/build && /nix/store/lc66gmgm58bbx4y5jjkqscriwvshp9fd-cmake-3.31.6/bin/cmake -P cmake_install.cmake
qttranslations> ninja: build stopped: subcommand failed.

Compiling with neoverse-n1 in gcc.tune, qttranslations failed in an odd way

like this

$ cat hello.c                      
#include <stdio.h>
int main() { printf("hello sizeof(void*) = %zd\n", sizeof(void*)); }
$ vim hello.c                
$ armv7l-unknown-linux-gnueabihf-gcc -o armhello -lrt -lpthread hello.c
$ qemu-arm
qemu: no user program specified
$ qemu-arm ./armhello 
hello sizeof(void*) = 4

like this

$ cat hello.c
#include <stdio.h>
int main() { printf("hello sizeof(void*) = %zd\n", sizeof(void*)); }
$ armv7l-unknown-linux-gnueabihf-gcc -o armhello -lrt -lpthread hello.c
$ qemu-arm ./armhello
hello sizeof(void*) = 4

So I simply tried nix-shell -p pkgsCross.armv7l-hf-multiplatform.stdenv.cc, if that is what you meant and got these errors:

/nix/store/viscj6hs10c5as7h53cxxw59yvgk505z-armv7l-unknown-linux-gnueabihf-binutils-2.43.1/bin/armv7l-unknown-linux-gnueabihf-ld: cannot find -lrt: No such file or directory
/nix/store/viscj6hs10c5as7h53cxxw59yvgk505z-armv7l-unknown-linux-gnueabihf-binutils-2.43.1/bin/armv7l-unknown-linux-gnueabihf-ld: cannot find -lpthread: No such file or direc
tory
/nix/store/viscj6hs10c5as7h53cxxw59yvgk505z-armv7l-unknown-linux-gnueabihf-binutils-2.43.1/bin/armv7l-unknown-linux-gnueabihf-ld: cannot find -lc: No such file or directory

So this turned out to work:

# flake.nix
{
  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
  };
  outputs = {nixpkgs, ...}: let
    system = "x86_64-linux";
    pkgs = import nixpkgs {
      inherit system;
      crossSystem = {
        config = "armv7l-linux-gnueabihf";
      };
    };
  in {
    devShells.${system}.default = import ./nix/shell.nix {inherit pkgs;};
  };
}

and

# nix/shell.nix
{pkgs, ...}:
pkgs.mkShell {
  buildInputs = [
    pkgs.glibc
    pkgs.glibc.static
  ];

  makeFlags = [
    "CC=${pkgs.stdenv.cc.targetPrefix}cc"
    "CXX=${pkgs.stdenv.cc.targetPrefix}g++"
  ];
}

with pkgs.glibc.static being the thing that made the difference