llvm-native: LLVM_USE_HOST_TOOLS=OFF to kill the native sub-build

Even with LLVM_TABLEGEN/CLANG_TABLEGEN provided, LLVM_USE_HOST_TOOLS defaults
ON when cross-compiling, so llvm/CMakeLists.txt creates the NATIVE external
project (llvm_create_cross_target LLVM NATIVE) — a full second HOST LLVM build
that inherits the Redox cross flags and died compiling native llvm-config.
We already supply the only native tools a cross-build needs (the tablegens),
so OFF eliminates the native sub-build entirely; LLVM uses the provided host
tblgens for .inc generation. Completes the llvm-native cross-build fix chain
(native-link, OPTIMIZED_TABLEGEN, LLVM_TABLEGEN var name, and now this).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

local/recipes/dev/llvm-native/recipe.toml

@@ -98,6 +98,15 @@ COOKBOOK_CMAKE_FLAGS+=(
     # LLVM 21.1.2). LLVM_OPTIMIZED_TABLEGEN=On would build a second optimized
     # native tblgen instead of using them. Off => LLVM uses what we provide.
     -DLLVM_OPTIMIZED_TABLEGEN=Off
+    # OFF is REQUIRED here. LLVM_USE_HOST_TOOLS defaults ON when cross-compiling
+    # and makes llvm/CMakeLists.txt create the NATIVE external project
+    # (llvm_create_cross_target LLVM NATIVE), a full second host LLVM build that
+    # inherits the Redox cross flags and dies compiling native llvm-config/etc.
+    # We already supply host-runnable, version-matched tblgens via
+    # LLVM_TABLEGEN/CLANG_TABLEGEN (the only native tools a cross-build needs),
+    # so the NATIVE project is pure waste. OFF => no native sub-build; LLVM uses
+    # the provided tblgens for .inc generation.
+    -DLLVM_USE_HOST_TOOLS=OFF
     -DLLVM_TARGET_ARCH=$ARCH
     -DLLVM_TOOLS_INSTALL_DIR=bin
     -DLLVM_UTILS_INSTALL_DIR=bin