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

From 86fc9ce2b381748813b372f7e86909be6f955cbd 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 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/emcc.py b/emcc.py
index 279f6d4d9..26e20e2cc 100644
--- a/emcc.py
+++ b/emcc.py
@@ -400,6 +400,9 @@ def get_cflags(user_args, is_cxx):
   # We add these to the user's flags (newargs), but not when building .s or .S assembly files
   cflags = get_clang_flags(user_args)
   cflags.append('--sysroot=' + cache.get_sysroot(absolute=True))
+  cflags.append('-resource-dir=@resourceDir@')
+  cflags.append('-idirafter' + cache.get_sysroot(absolute=True) + os.path.join('/include'))
+  cflags.append('-iwithsysroot' + os.path.join('/include','c++','v1'))
 
   if settings.EMSCRIPTEN_TRACING:
     cflags.append('-D__EMSCRIPTEN_TRACING__=1')
-- 
2.42.0