Initial stub of a Makefile and patches for LLVM

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

patches/llvm/0023-clang-error-when-using-ifunc-attribute-on-unsupporte.patch

@@ -0,0 +1,31 @@
+From 6838a67da41425e2268ce7b4e807669986c3699e Mon Sep 17 00:00:00 2001
+From: q66 <q66@chimera-linux.org>
+Date: Fri, 29 Nov 2024 19:46:27 +0100
+Subject: [PATCH 23/29] clang: error when using ifunc attribute on unsupported
+ targets
+
+---
+ clang/lib/Sema/SemaDeclAttr.cpp | 7 +++++++
+ 1 file changed, 7 insertions(+)
+
+diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
+index f351663c6..7138d953b 100644
+--- a/clang/lib/Sema/SemaDeclAttr.cpp
++++ b/clang/lib/Sema/SemaDeclAttr.cpp
+@@ -1721,6 +1721,13 @@ static void handleIFuncAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+     return;
+   }
+ 
++  // Unsupported targets should raise a diagnostic error.
++  if (!S.Context.getTargetInfo().supportsIFunc()) {
++    S.Diag(AL.getLoc(), diag::err_keyword_not_supported_on_target)
++      << AL << AL.getRange();
++    return;
++  }
++
+   markUsedForAliasOrIfunc(S, D, AL, Str);
+   D->addAttr(::new (S.Context) IFuncAttr(S.Context, AL, Str));
+ }
+-- 
+2.49.0
+