From 54a487505a9c14fa4271ac6858a2af8c23eecbd0 Mon Sep 17 00:00:00 2001
From: Robert Scott <code@humanleg.org.uk>
Date: Fri, 26 Nov 2021 22:12:42 +0000
Subject: [PATCH] llvmPackages_13.libcxx: require gcc >=10 on gcc platforms

specifically aarch64. as of version 13 libcxx does not build on gcc9.
---
 pkgs/development/compilers/llvm/13/default.nix | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/pkgs/development/compilers/llvm/13/default.nix b/pkgs/development/compilers/llvm/13/default.nix
index 13be73967143..6c87366ea315 100644
--- a/pkgs/development/compilers/llvm/13/default.nix
+++ b/pkgs/development/compilers/llvm/13/default.nix
@@ -244,7 +244,12 @@ let
       inherit llvm_meta;
       stdenv = if stdenv.hostPlatform.useLLVM or false
                then overrideCC stdenv buildLlvmTools.clangNoLibcxx
-               else stdenv;
+               else (
+                 # libcxx >= 13 does not build on gcc9
+                 if stdenv.cc.isGNU && lib.versionOlder stdenv.cc.version "10"
+                 then pkgs.gcc10Stdenv
+                 else stdenv
+               );
     };
 
     libcxxabi = callPackage ./libcxxabi {