Initial stub of a Makefile and patches for LLVM

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

patches/llvm/0019-clang-default-to-fno-semantic-interposition.patch

@@ -0,0 +1,27 @@
+From a30a86b7eb59e7ec5baace8e7252d38d7f8e15ed Mon Sep 17 00:00:00 2001
+From: q66 <q66@chimera-linux.org>
+Date: Sat, 4 Nov 2023 09:11:58 +0100
+Subject: [PATCH 19/29] clang: default to -fno-semantic-interposition
+
+---
+ clang/lib/Driver/ToolChains/Clang.cpp | 4 +---
+ 1 file changed, 1 insertion(+), 3 deletions(-)
+
+diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
+index 57b7d2bd4..417b85899 100644
+--- a/clang/lib/Driver/ToolChains/Clang.cpp
++++ b/clang/lib/Driver/ToolChains/Clang.cpp
+@@ -5824,9 +5824,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
+       // The supported targets need to call AsmPrinter::getSymbolPreferLocal.
+       bool SupportsLocalAlias =
+           Triple.isAArch64() || Triple.isRISCV() || Triple.isX86();
+-      if (!A)
+-        CmdArgs.push_back("-fhalf-no-semantic-interposition");
+-      else if (A->getOption().matches(options::OPT_fsemantic_interposition))
++      if (A && A->getOption().matches(options::OPT_fsemantic_interposition))
+         A->render(Args, CmdArgs);
+       else if (!SupportsLocalAlias)
+         CmdArgs.push_back("-fhalf-no-semantic-interposition");
+-- 
+2.49.0
+