Initial stub of a Makefile and patches for LLVM

Nothing much, but getting some patches from chimera linux that should
work.

patches/llvm/0006-compiler-rt-default-to-libc-for-sanitizers.patch

@@ -0,0 +1,25 @@
+From 73de90029db874f0fe7c97b11692a7534f2e5f70 Mon Sep 17 00:00:00 2001
+From: q66 <q66@chimera-linux.org>
+Date: Sat, 4 Nov 2023 08:55:34 +0100
+Subject: [PATCH 06/29] compiler-rt: default to libc++ for sanitizers
+
+---
+ compiler-rt/CMakeLists.txt | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/compiler-rt/CMakeLists.txt b/compiler-rt/CMakeLists.txt
+index 2c52788de..bad897a12 100644
+--- a/compiler-rt/CMakeLists.txt
++++ b/compiler-rt/CMakeLists.txt
+@@ -228,7 +228,7 @@ macro(handle_default_cxx_lib var)
+       set(${var}_LIBNAME "libc++")
+       set(${var}_INTREE 1)
+     else()
+-      set(${var}_LIBNAME "libstdc++")
++      set(${var}_LIBNAME "libc++")
+       set(${var}_SYSTEM 1)
+     endif()
+   else()
+-- 
+2.49.0
+