https://github.com/chimera-linux/cports/blob/master/main/libtool/patches/cxx-clang-runtimes.patch
https://lists.gnu.org/archive/html/libtool-patches/2021-10/msg00016.html
https://git.savannah.gnu.org/cgit/libtool.git/commit/?id=1d2577357ee704da2d6d7c7da119ad82ba8ca172
https://git.savannah.gnu.org/cgit/libtool.git/commit/?id=6132006b5fb6b95f31c30a972fbb829f93e1878b

https://bugs.gentoo.org/914068

From 969258b1b25b5b0f78a2a0a2427c4dd4b038f13f Mon Sep 17 00:00:00 2001
From: q66 <q66@chimera-linux.org>
Date: Sat, 3 Sep 2022 09:41:45 +0000
Subject: [PATCH] permit clang builtins library to be linked in

libtool links c++ stuff with -nostdlib and manually extracts the
allowed libs, but this did not previously cover the clang runtimes
and broke builds on some targets where builtins are needed.

diff --git a/m4/libtool.m4 b/m4/libtool.m4
index 79a2451..9c08481 100644
--- a/m4/libtool.m4
+++ b/m4/libtool.m4
@@ -7554,7 +7554,7 @@ if AC_TRY_EVAL(ac_compile); then
   for p in `eval "$output_verbose_link_cmd"`; do
     case $prev$p in
 
-    -L* | -R* | -l*)
+    -L* | -R* | -l* | */libclang_rt*.a)
        # Some compilers place space between "-{L,R}" and the path.
        # Remove the space.
        if test x-L = "$p" ||
-- 
2.34.1