nixpkgs/pkgs/development/compilers/emscripten/0001-emulate-clang-sysroot-include-logic.patch

From 67f54fde2b1683aae3800f7a86a4e507c1125be8 Mon Sep 17 00:00:00 2001
From: Yureka <yuka@yuka.dev>
Date: Sat, 7 Aug 2021 09:16:46 +0200
Subject: [PATCH] emulate clang 'sysroot + /include' logic

Authored-By: Alexander Khovansky <alex@khovansky.me>
Co-Authored-By: Yureka <yuka@yuka.dev>

Clang provided by nix patches out logic that appends 'sysroot + /include'
to the include path as well as automatic inclusion of libcxx includes (/include/c++/v1).
The patch below adds that logic back by introducing cflags emulating this behavior to emcc
invocations directly.

Important note: with non-nix clang, sysroot/include dir ends up being the last
in the include search order, right after the resource root.
Hence usage of -idirafter. Clang also documents an -isystem-after flag
but it doesn't appear to work
---
 emcc.py | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/emcc.py b/emcc.py
index 999314afc..0e23c066c 100755
--- a/emcc.py
+++ b/emcc.py
@@ -759,7 +759,12 @@ def emsdk_ldflags(user_args):
 
 
 def emsdk_cflags(user_args):
-  cflags = ['--sysroot=' + shared.Cache.get_sysroot(absolute=True)]
+  cflags = [
+    '--sysroot=' + shared.Cache.get_sysroot(absolute=True),
+    '-resource-dir=@resourceDir@',
+    '-idirafter' + shared.Cache.get_sysroot(absolute=True) + os.path.join('/include'),
+    '-iwithsysroot' + os.path.join('/include','c++','v1')
+  ]
 
   def array_contains_any_of(hay, needles):
     for n in needles:
-- 
2.32.0