Code change:
<ins> { lib, stdenvNoLibs, buildPackages , gcc, glibc , libiberty }: let gccConfigureFlags = gcc.cc.configureFlags ++ [ "--disable-fixincludes" "--disable-intl" "--enable-threads=posix" "--with-glibc-version=${glibc.version}" # these are required in order to prevent inhibit_libc=true, # which will cripple libgcc's unwinder; see: #  https://github.com/NixOS/nixpkgs/issues/213453#issuecomment-1616346163 "--with-headers=${lib.getDev glibc}/include" "--with-native-system-header-dir=${lib.getDev glibc}${glibc.incdir or "/include"}" "--with-build-sysroot=/" ]; in stdenvNoLibs.mkDerivation (finalAttrs: { pname = "libgcc"; inherit (gcc.cc) src version; outputs = [ "out" "dev" ]; strictDeps = true; depsBuildBuild = [ buildPackages.stdenv.cc ]; nativeBuildInputs = [ libiberty ]; buildInputs = [ glibc ]; postUnpack = '' mkdir -p ./build buildRoot=$(readlink -e "./build") ''; postPatch = gcc.cc.passthru.forceLibgccToBuildCrtStuff + '' sourceRoot=$(readlink -e "./libgcc") ''; hardeningDisable = [ "pie" ]; preConfigure = '' # Drop in libiberty, as external builds are not expected cd "$buildRoot" ( mkdir -p build-${stdenvNoLibs.buildPlatform.config}/libiberty/ cd build-${stdenvNoLibs.buildPlatform.config}/libiberty/ ln -s ${buildPackages.libiberty}/lib/libiberty.a ./ ) mkdir -p "$buildRoot/gcc" cd "$buildRoot/gcc" ( # We "shift" the tools over to fake platforms perspective from the previous stage. export AS_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$AS_FOR_BUILD export CC_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$CC_FOR_BUILD export CPP_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$CPP_FOR_BUILD export CXX_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$CXX_FOR_BUILD export LD_FOR_BUILD=${buildPackages.stdenv.cc.bintools}/bin/$LD_FOR_BUILD export AS=$AS_FOR_BUILD export CC=$CC_FOR_BUILD export CPP=$CPP_FOR_BUILD export CXX=$CXX_FOR_BUILD export LD=$LD_FOR_BUILD export AS_FOR_TARGET=${stdenvNoLibs.cc}/bin/$AS export CC_FOR_TARGET=${stdenvNoLibs.cc}/bin/$CC export CPP_FOR_TARGET=${stdenvNoLibs.cc}/bin/$CPP export LD_FOR_TARGET=${stdenvNoLibs.cc.bintools}/bin/$LD # We define GENERATOR_FILE so nothing bothers looking for GNU GMP. export NIX_CFLAGS_COMPILE_FOR_BUILD+=' -DGENERATOR_FILE=1' "$sourceRoot/../gcc/configure" ${lib.concatStringsSep " " gccConfigureFlags} # We remove the `libgcc.mvar` deps so that the bootstrap xgcc isn't built. sed -e 's,libgcc.mvars:.*$,libgcc.mvars:,' -i Makefile make  config.h  libgcc.mvars  tconfig.h  tm.h  options.h  insn-constants.h  insn-modes.h ) mkdir -p "$buildRoot/gcc/include" # Preparing to configure + build libgcc itself mkdir -p "$buildRoot/gcc/${stdenvNoLibs.hostPlatform.config}/libgcc" cd "$buildRoot/gcc/${stdenvNoLibs.hostPlatform.config}/libgcc" configureScript=$sourceRoot/configure chmod +x "$configureScript" export AS_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$AS_FOR_BUILD export CC_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$CC_FOR_BUILD export CPP_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$CPP_FOR_BUILD export CXX_FOR_BUILD=${buildPackages.stdenv.cc}/bin/$CXX_FOR_BUILD export LD_FOR_BUILD=${buildPackages.stdenv.cc.bintools}/bin/$LD_FOR_BUILD export AS=${stdenvNoLibs.cc}/bin/$AS export CC=${stdenvNoLibs.cc}/bin/$CC export CPP=${stdenvNoLibs.cc}/bin/$CPP export CXX=${stdenvNoLibs.cc}/bin/$CXX export LD=${stdenvNoLibs.cc.bintools}/bin/$LD export AS_FOR_TARGET=${stdenvNoLibs.cc}/bin/$AS_FOR_TARGET export CC_FOR_TARGET=${stdenvNoLibs.cc}/bin/$CC_FOR_TARGET export CPP_FOR_TARGET=${stdenvNoLibs.cc}/bin/$CPP_FOR_TARGET export LD_FOR_TARGET=${stdenvNoLibs.cc.bintools}/bin/$LD_FOR_TARGET ''; configurePlatforms = [ "build" "host" ]; configureFlags = [ "cross_compiling=true" "--disable-gcov" "--with-glibc-version=${glibc.version}" ]; makeFlags = [ "MULTIBUILDTOP:=../" ]; postInstall = '' moveToOutput "lib/gcc/${stdenvNoLibs.hostPlatform.config}/${finalAttrs.version}/include" "$dev" mkdir -p "$out/lib" "$dev/include" ln -s "$out/lib/gcc/${stdenvNoLibs.hostPlatform.config}/${finalAttrs.version}"/* "$out/lib" ln -s "$dev/lib/gcc/${stdenvNoLibs.hostPlatform.config}/${finalAttrs.version}/include"/* "$dev/include/" ''; }) </ins>

Related discussion:
text: Especially since the failure mode gives the user no error message to help them troubleshoot the problem! is a great candidate for this since it's one of those very rare non-C++ programs that uses advanced stack-unwinding features from pthreads.
Confirming fixes the issue. Tested with both and on real hardware and with QEMU on x86_64.
~I think this is fixed, and more cleanly,~ by Edit: it is not. :frowning_face: I will keep trying. Test is in Currently building.
Added this to , but commented out since it is not fixed yet.