From 486e12ad685be4c0dc5e3033bc1c69f0146b0a99 Mon Sep 17 00:00:00 2001
From: sternenseemann <0rpkxez4ksa01gb3typccl0i@systemli.org>
Date: Thu, 15 Apr 2021 00:42:15 +0200
Subject: [PATCH] llvmPackages_7.libcxxabi: take libunwind as an optional
 dependency again

This reverts commit 76b54c75b3bc7a17ffaa20a862246f1d7fe89b58 and brings
llvmPackages_7.libcxxabi in line with what the other llvmPackages
sets are doing again (with llvmPackages_7 being the sole outlier).

This also fixes an evaluation error of llvmPackages_7.libcxxabi if
stdenv.hostPlatform.useLLVM is true as the nonexistant libunwind
argument would be overridden.
---
 .../compilers/llvm/7/libc++abi/default.nix           | 12 +++++++-----
 1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/pkgs/development/compilers/llvm/7/libc++abi/default.nix b/pkgs/development/compilers/llvm/7/libc++abi/default.nix
index 84c47865141..9f9606f586c 100644
--- a/pkgs/development/compilers/llvm/7/libc++abi/default.nix
+++ b/pkgs/development/compilers/llvm/7/libc++abi/default.nix
@@ -1,5 +1,5 @@
-{ lib, stdenv, cmake, fetch, libcxx, llvm, version
-, standalone ? false
+{ lib, stdenv, cmake, fetch, libcxx, libunwind, llvm, version
+, standalone ? stdenv.hostPlatform.useLLVM or false
   # on musl the shared objects don't build
 , enableShared ? !stdenv.hostPlatform.isStatic
 }:
@@ -11,6 +11,7 @@ stdenv.mkDerivation {
   src = fetch "libcxxabi" "1zcqxsdjhawgz1cvpk07y3jl6fg9p3ay4nl69zsirqb2ghgyhhb2";
 
   nativeBuildInputs = [ cmake ];
+  buildInputs = lib.optional (!stdenv.isDarwin && !stdenv.isFreeBSD && !stdenv.hostPlatform.isWasm) libunwind;
 
   postUnpack = ''
     unpackFile ${libcxx.src}
@@ -22,9 +23,10 @@ stdenv.mkDerivation {
     patch -p1 -d $(ls -d libcxx-*) -i ${../../libcxx-0001-musl-hacks.patch}
   '';
 
-  cmakeFlags =
-     lib.optional standalone "-DLLVM_ENABLE_LIBCXX=ON" ++
-     lib.optional (!enableShared) "-DLIBCXXABI_ENABLE_SHARED=OFF";
+  cmakeFlags = lib.optionals standalone [
+    "-DLLVM_ENABLE_LIBCXX=ON"
+    "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
+  ] ++ lib.optional (!enableShared) "-DLIBCXXABI_ENABLE_SHARED=OFF";
 
   installPhase = if stdenv.isDarwin
     then ''